U.S. patent application number 10/689547 was filed with the patent office on 2004-09-09 for nanometer-scale engineered structures, methods and apparatus for fabrication thereof, and applications to mask repair, enhancement, and fabrications.
This patent application is currently assigned to NanoInk, Inc.. Invention is credited to Amro, Nabil, Crocker, Percy Van, Cruchon-Dupeyrat, Sylvain, Demers, Linette, Disawal, Sandeep, Elghanian, Robert, Zhang, Hua.
Application Number | 20040175631 10/689547 |
Document ID | / |
Family ID | 32176479 |
Filed Date | 2004-09-09 |
United States Patent
Application |
20040175631 |
Kind Code |
A1 |
Crocker, Percy Van ; et
al. |
September 9, 2004 |
Nanometer-scale engineered structures, methods and apparatus for
fabrication thereof, and applications to mask repair, enhancement,
and fabrications
Abstract
Photomask repair and fabrication with use of direct-write
nanolithography, including use of scanning probe microscopic tips
for deposition of ink materials including sol-gel and metallic
inks. Additive methods can be combined with substractive methods.
Holes can be filled with nanostructures. Height of the
nanostructure filling the hole can be controlled without losing
control of the lateral dimensions of the nanostructure.
Chrome-on-Glass masks can be used and fabricated, as well as more
advanced masks including masks for nanoimprint nanolithography.
Inventors: |
Crocker, Percy Van;
(Chicago, IL) ; Cruchon-Dupeyrat, Sylvain;
(Chicago, IL) ; Demers, Linette; (Chicago, IL)
; Elghanian, Robert; (Chicago, IL) ; Disawal,
Sandeep; (Chicago, IL) ; Amro, Nabil;
(Chicago, IL) ; Zhang, Hua; (Chicago, IL) |
Correspondence
Address: |
FOLEY AND LARDNER
SUITE 500
3000 K STREET NW
WASHINGTON
DC
20007
US
|
Assignee: |
NanoInk, Inc.
|
Family ID: |
32176479 |
Appl. No.: |
10/689547 |
Filed: |
October 21, 2003 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
60419781 |
Oct 21, 2002 |
|
|
|
Current U.S.
Class: |
430/5 ; 378/35;
430/4; 850/16; 850/33 |
Current CPC
Class: |
C23C 18/161 20130101;
C09D 11/52 20130101; C23C 18/143 20190501; C23C 18/1658 20130101;
Y10S 977/857 20130101; C23C 18/1612 20130101; C23C 18/1605
20130101; C23C 18/06 20130101; C23C 18/145 20190501; G03F 1/72
20130101; C23C 18/1254 20130101; Y10S 977/863 20130101; G03F 7/0002
20130101; C23C 18/1208 20130101 |
Class at
Publication: |
430/005 ;
430/004; 378/035 |
International
Class: |
G03F 009/00; G21K
005/00 |
Claims
What is claimed is:
1. a method for additive mask repair in the semiconductor industry
with fine control over lateral dimensions and height comprising:
depositing material to a defective mask by direct write
nanolithography from a tip for additive repair.
2. the method according to claim 1, wherein the defective mask
comprises an optically transparent substrate containing thereon a
mask layer which is an optically opaque pattern.
3. the method according to claim 1, wherein the defective mask is a
phase shifting photomask.
4. the method according to claim 1, wherein the defective mask is
an EUV lithography mask, an electron projection lithography mask,
an x-ray lithography mask, or an ion projection lithography
mask.
5. the method according to claim 1, wherein the defective mask is
for nanoimprint lithography.
6. the method according to claim 1, wherein the defective mask
comprises an opaque defect.
7. the method according to claim 1, wherein the defective mask
comprises a clear defect.
8. the method according to claim 1, wherein the defective mask
comprises a nanometer scale opening to which the material is
added.
9. the method according to claim 1, wherein the defective mask
comprises an opening having a lateral dimension of less than about
100 nm to which the material is added.
10. the method according to claim 1, wherein the defective mask
comprises an opening having a lateral dimension of less than about
80 nm to which the material is added.
11. the method according to claim 1, wherein the defective mask
comprises an opening having a lateral dimension of less than about
56 nm to which the material is added.
12. the method according to claim 1, wherein the defective mask
comprises an opening having a lateral dimension of less than about
35 nm to which the material is added.
13. the method according to claim 1, wherein the mask comprises a
feature of about 100 nm or less in lateral dimension which is
repaired.
14. the method according to claim 1, wherein the tip is a scanning
probe microscope tip.
15. the method according to claim 1, wherein the tip is an atomic
force microscope tip.
16. the method according to claim 1, wherein the tip is a hollow
tip.
17. the method according to claim 1, wherein the material is an
optically transparent material.
18. the method according to claim 1, wherein the material is an
optically opaque material.
19. the method according to claim 1, wherein the material is
applied as multiple layers.
20. the method according to claim 1, wherein the material is
applied to a height of at least 30 nm.
21. the method according to claim 1, wherein the material is
applied to a height of at least 45 nm.
22. the method according to claim 1, wherein the material is
applied to a height of at least 100 nm.
23. the method according to claim 1, wherein the material is
applied to a height of at least 150 nm.
24. the method according to claim 1, wherein the material is a
sol-gel material.
25. the method according to claim 1, wherein the material is a
metal oxide or glass, or precursors thereof.
26. the method according to claim 1, wherein the material is a
metallic material or a metallic precursor.
27. the method according to claim 1, wherein the material is an
opaque carbon material or a precursor therefor.
28. the method according to claim 1, wherein the material comprises
nanoparticles.
29. the method according to claim 1, wherein the material comprises
one or more high molecular weight compounds.
30. the method according to claim 1, wherein the material has
similar optical properties to the pattern to which it is added.
31. the method of claim 1, wherein the adding step is carried out
without vacuum conditions.
32. the method of claim 1, wherein the adding step is repeated with
the same material.
33. the method of claim 1, wherein the adding step is repeated with
different materials.
34. the method of claim 1, further comprising one or more
post-adding steps comprising external heating, light irradiation,
sonic excitation, or chemical reaction by exposure to a vapor or
liquid.
35. the method according to claim 1, wherein the adding step is
carried out as one of a series of adding steps carried out with a
plurality of tips.
36. the method according to claim 1, further comprising subtracting
material from the defective mask.
37. the method according to claim 1, wherein the subtracting of
material is carried out with use of a tip.
38. the method according to claim 1, wherein the subtracting of
material is carried out with use of a scanning probe microscope
tip.
39. the method according to claim 1, wherein the subtracting of
material is carried out with use of an atomic force microscope
tip.
40. a method for nanolithography comprising: (1) providing a mask,
(2) providing a scanning probe microscope tip, wherein the tip is
coated with a patterning compound, (3) contacting the coated tip
with the mask so that the compound is applied to the mask.
41. the method according to claim 40, wherein the tip is an atomic
force microscope tip.
42. the method according to claim 40, wherein the tip is a hollow
tip.
43. the method according to claim 40, wherein the patterning
compound is a sol-gel material.
44. the method according to claim 40, wherein the patterning
compound comprises a metal.
45. the method according to claim 40, wherein the contacting step
is repeated to form a multilayer structure.
46. the method according to claim 40, further comprising
subtracting material from the mask.
47. a method for nanolithography comprising: (1) providing a
substrate having at least one defect, (2) providing a tip with a
patterning compound, (3) using the tip with the substrate so that
the compound is applied to the substrate at the defect to repair
the defect.
48. the method according to claim 47, wherein the tip is an atomic
force microscope tip.
49. the method according to claim 47, wherein the tip is a hollow
tip.
50. the method according to claim 47, wherein the patterning
compound is a sol-gel material or a metal.
51. a method for mask fabrication comprising adding material to a
substrate to form a mask by direct write nanolithography with use
of a scanning probe microscopic tip to pattern material on the
substrate.
52. the method according to claim 51, wherein the tip is an atomic
force microscope tip.
53. the method according to claim 51, wherein the tip is a hollow
tip.
54. the method according to claim 51, wherein the material is an
opaque material.
55 the method according to claim 51, wherein the material is a
transparent material.
56. the method according to claim 51, wherein the material
comprises a metal.
57. the method according to claim 51, wherein the mask is a
photomask.
58. the method according to claim 51, wherein the mask is an EUV
lithography mask, an electron projection lithography mask, an x-ray
lithography mask, or an ion projection lithography mask.
59. the method according to claim 51, wherein the material is
patterned on the substrate to a height of at least 10 nm.
60. the method according to claim 51, wherein the material is
patterned on the substrate to a height of at least 100 nm.
61. a method for nanolithography comprising using a coated atomic
force microscope tip to deposit a patterning compound on a
substrate in mask fabrication.
62. the method according to claim 61, wherein the mask is a mask
for nanolithography.
63. the method according to claim 61, wherein the patterning
compound is deposited to a height of at least 100 nm.
64. the method according to claim 61, wherein the material is a
sol-gel material or a metal.
65. the method according to claim 61, wherein the patterning
compound is deposited more than once to form a multi-layered
deposit.
66. a method of nanolithography comprising using a tip to layer one
or more patterning compounds on a substrate so the one or more
patterning compounds form a structure at least about 10 nm
high.
67. the method according to claim 66, wherein the structure is a
mask enhancement structure.
68. the method according to claim 66, wherein the structure is at
least about 45 nm high.
69. the method according to claim 66, wherein the structure is at
least about 100 nm high.
70. the method according to claim 66, wherein the structure is
about 10 nm to about 250 nm high.
71. the method according to claim 66, wherein the structure is a
single layer.
72. the method according to claim 66, wherein the structure
comprises multiple layers.
73. the method according to claim 66, wherein the compounds are
sol-gel compounds or metallic compounds.
74. a repaired mask prepared by the method of claim 1.
75. a repaired mask prepared by the method of claim 40.
76. a repaired mask prepared by the method of claim 47.
77. a mask fabricated by the method of claim 51.
78. a mask fabricated by the method of claim 61.
79. Method of use of a scanning probe microscope to repair a mask
by additive repair.
80. the method of use according to claim 79, wherein the scanning
probe microscope is an atomic force microscope.
81. Method of use of an scanning probe microscope to prepare a mask
by additive lithography.
82. the method of use according to claim 81, wherein the scanning
probe microscope is an atomic force microscope.
83. a method comprising the steps of: inspecting an object by
making SPM measurement of the object with a first SPM probe;
repairing the object by adding material to the object's material
with the first SPM probe or with a second SPM probe, wherein the
adding of material is carried out by direct write nanolithographic
printing by transfer of the material from the probe tip to the
object.
84. a repaired mask comprising: a defective mask substrate
comprising at least one nanometer-scale opening which is a defect;
at least one additive repair nanostructure at least partially
filling the opening.
85. the mask according to claim 84, wherein the nanostructure
substantially fills the opening.
86. the mask according to claim 84, wherein the nanometer scale
opening has a lateral dimension of about 100 nm or less.
87. the mask according to claim 84, wherein the nanometer scale
opening has a lateral dimension of about 80 nm or less.
88. the mask according to claim 84, wherein the nanometer scale
opening has a lateral dimension of about 56 nm or less.
89. the mask according to claim 84, wherein the nanometer scale
opening has a depth of about 500 nm or less.
90. the mask according to claim 84, wherein the nanometer scale
opening has a depth of about 100 nm or less.
91. the mask according to claim 84, wherein the additive repair
structure is a sol-gel structure.
92. the mask according to claim 84, wherein the additive repair
structure is a metallic structure.
93. the mask according to claim 84, wherein the additive repair
structure is a carbon structure.
94. the mask according to claim 84, wherein the additive repair
structure is substantially the same material as the mask
substrate.
95. the mask according to claim 84, wherein the additive repair
structure is a different material from the mask substrate.
96. a single layer nanostructure having a height of at least 100 nm
and a lateral dimension of about 200 microns or less.
97. a multiple layer nanostructure having a height of at least 100
nm and a lateral dimension of about 200 microns or less.
Description
RELATED APPLICATIONS
[0001] This application claims priority benefit to provisional
application 60/419,781 filed Oct. 21, 2002 to Crocker et al.
("Nanometer-scale engineered structures, methods and apparatus for
fabrication thereof, and applications to photomask repair and
enhancement"), which is hereby incorporated by reference in its
entirety.
INTRODUCTION
[0002] The present invention relates in general to the engineering
of nanometer-scale structures and, in particular, the repair and
fabrication of masks used for lithography. Applications include the
semiconductor industry.
[0003] Masks including photomasks are important to the
semiconductor industry. Photomask fabrication and repair is an
important technology in the semiconductor industry for
microchip/integregrated circuit (IC) production by
microlithography. See, for example, Handbook of Microlithography,
Micromachining, and Microfabrication, Vol. I and II, including Vol.
I, Chapter 5 "Photomask Fabrication Procedures and Limitations" by
Skinner et al. (pages 377-474). A typical photomask (or reticle)
used in conventional deep-UV optical lithography comprises an
optically transparent substrate containing thereon a mask layer
which is an optically opaque pattern. Light passes through the
non-opaque regions only, generating a pattern below the photomask.
In other words, the mask is illuminated, projecting an image on a
wafer coated with a photoresist. Typically, photomasks are
expensive and complex, and some photomasks contain defects. There
exists, therefore, a strong economic incentive to repair these
defects.
[0004] Common mask defects, as illustrated in FIG. 1, for example,
are classified by their influence on the aerial image (the optical
pattern that is generated by illumination through the mask):
[0005] 1--Opaque defects, which are extraneous (spurious) features
typically to be repaired by a subtractive method; for example, they
include opaque spots or blobs in areas to be left transparent,
unwanted necks or bridges between features, unwanted spikes or
protuberances on the side of features.
[0006] 2--Clear defects, which are missing or incomplete features,
typically to be repaired by an additive method; they include
pin-holes, broken or thinned lines, notches, and corner
defects.
[0007] Defects may occur in the mask layer (e.g. Cr metal or
MoSi.sub.2) or in the substrate (e.g. quartz bumps or divots).
[0008] Mask defects can further be classified as hard vs. soft
defects, as disclosed in the aforementioned Skinner article. A soft
defect is typically any defect that can be removed by a cleaning
process, whereas a hard defect cannot be removed by a cleaning
process. Typically, for example, particles, contamination, residue,
stains, etc. on the chrome/quartz would be called soft defects.
Also, missing or extra features in the chrome/absorber/phase
shifter (see below) pinholes, quartz pits, etc. would be called
hard defects. Types of hard defects include, for example, pinholes,
pinspots, intrusions, corner defects, missing features, absorber
transmission defects, protrusions, and semi-transparent defect in a
clear area.
[0009] Other types of defects include those that result from errors
in the original mask data tape and also mask misprocessing
(misplacement and missizing of geometries; those that result from
CD (critical dimension) variations across the masks and edge
quality of features, i.e., line edge roughness.
[0010] In the present invention, these and other types of defects
can be repaired by improved means of nanolithography and
nanodeposition which, among other things, can add material to the
mask, or can add materials to and substract materials from the
mask. In addition, mask features can be enhanced to include
features that may improve performance (e.g., resolution) but are
not necessarily patterned or printed. Enhancement features can be,
for example, 100 nm structures or less in lateral dimension.
[0011] The present invention relates to nanometer-scale deposition
and removal methods that use direct write deposition
nanolithography, including nanolithography based on scanning probe
microscopic methods and atomic force microscopic methods, and
especially DIP PEN NANOLITHOGRAPHY.TM. (DPN.TM.) printing and
deposition methods, as an important step (DPN.TM. and DIP PEN
NANOLITHOGRAPHY.TM. are trademarks of NanoInk, Inc., Chicago,
Ill.). The DPN.TM. deposition and printing methods are disclosed
for example in (1) U.S. Patent Publication No. 2002/0063212 A1
published to Mirkin et al. on May 30, 2002, and (2) U.S. Patent
Publication No. 2002/0122873 A1 published to Mirkin et al. on Sep.
5, 2002, the complete disclosures of which are hereby incorporated
by reference, particularly for the experimental parameters for the
nanolithography, including substrates, inks, patterning compounds,
tip, instrumentation, software, and the like, and the variety of
embodiments and applications which can be carried out.
[0012] The present invention further relates to (1) the
afore-mentioned methods; (2) the apparatus implementing or enabling
them; and (3) the articles produced by these methods, which are
engineered nanometer-scale features placed with nanometer-scale
precision.
[0013] More particularly, the present invention relates to the use
of the afore-mentioned articles, methods and apparatus to (a)
fabricate, repair, and enhance masks and photomasks; (b) modify
microelectronic devices or microsystems (MEMS), and (c) to create
masks, microelectronic devices or MEMS. The acronym "MEMS" for
purposes of the present disclosure can encompass all microsystems,
whether microelectromechanical, microelectrooptical,
microelectromagnetic, microfluidic . . . in nature, and
disregarding their critical dimension (i.e. including
nanoelectromechanical systems, NEMS).
[0014] Microchips are most commonly commercially produced using
optical lithography, a process in which a photosensitive resist is
spun on the substrate to pattern and then selectively exposed by UV
light through a photomask or reticle. The need for more
sophisticated, faster and denser devices has reduced the minimum
feature size in microchips (the critical dimension, CD) by a 0.7
factor every three years--a model known as Moore's law
["International Roadmap for Semiconductors (Lithography)",
International SEMATEC, 2000]. The minimum feature size and spacing
in the photomasks used to fabricate them has shrunk proportionally.
However, photomask feature dimensions are currently approaching
their theoretical physical limit. Quantum effects such as tunneling
and particle-wave interference effects can become important for
device performance as shrinking continues to nanometer scales.
Photomasks are thus increasingly precise, complex (with the
addition of optical phase correction (OPC) and the use of
techniques such as phase shifting and off-axis illumination, OAI)
and therefore increasingly expensive, for example, typically above
$50,000 per unit for alternating phase shift masks. A different
photomask is required for each lithography exposure, in other words
for each layer in the microchip. More than a dozen masks may be
required for some designs. Lithography thus represents one of the
largest fixed costs associated with chip production (typically,
approx. 1/3 of the total). The total cost for a 90-nm mask can be
about one million dollars.
[0015] In addition, even minor defects on the photomasks may result
in a global failure of the resulting microchips or may reduce
dramatically their mean time before failure. For example, a single
extraneous opaque imperfection located between two printed lines on
the photomask may result in an electrical short between two
electrical paths, triggering a major defect or breakdown of the
whole chip. Given the expenses and stringent quality requirements
associated with photomasks, it is economically advantageous to (a)
repair masks presenting defects after fabrication or after use; (b)
modify masks otherwise rendered unusable because of a minor error
at design time. It is also important to consider cheaper, more
reliable alternatives to current photomask fabrication methods.
[0016] Currently used photomask repair processes are either
extremely expensive, limited, or not well adapted to advanced mask
technologies. The most commonly used tool, focused ion beam (FIB),
which is capable of etching opaque defects and filling clear ones
with carbon or metal deposits [see, for example, Tao et al., U.S.
Pat. No. 5,104,684, 1992], and may cost above $5M per unit (see
e.g. Veeco FEI commercial instruments). While this technology can
work for COG (chromium on glass), despite poor edge placement
accuracy, repair technologies based on gallium staining are known
to damage the areas surrounding the defect in attenuating phase
shifting masks. Laser ablation and laser-assisted deposition is
also used [see for example Balz et al., U.S. Pat. No.
5,441,386,1995 and references therein] [Segal et al., U.S. Pat. No.
4,200,668 1980] [Chiba et al., Japanese Journal of Applied Physics
part 1 38 (12A): 6577-6582,1999 and references therein].
[0017] Less costly but purely subtractive photomask repair tools
based upon scanning probe microscopy are also available (See for
example instruments being commercialized by Rave LLC, and U.S. Pat.
No. 6,353,219 to Kley (Mar. 5, 2002)). A nanobit, i.e. a cantilever
with a high force constant terminated by a sharp, resilient tip,
can be used to mechanically scratch away the spurious parts. Thus
far, additive repair with this tool can only be accomplished by
successive deposition of large carbon patches using e.g. focused
ion beam (FIB) and then trimming of excess material from the patch.
Similar subtractive-only technology using a laser beam delivered by
a scanning near-field optical microscopy probe is being developed
(Instruments developed by Nanonics, Israel).
[0018] There is therefore a need to develop a technology that will
be capable of both additive and subtractive repair, while
maintaining the cost and precision advantages of e.g.
nanomachining. In the following sections, it is demonstrated that
such alternative can be developed using deposition nanolithography
techniques, such as Dip Pen.TM. Nanolithographic printing, as a
preferred patterning method.
[0019] Current reticle technologies include binary photomasks
(Chromium on glass, COG) and phase shifting masks. Binary
photomasks are typically fabricated by deposition of opaque
metallic chromium (or aluminum or nickel) on a transparent
substrate (e.g. quartz, sapphire, glass). A typical process for
binary chromium masks starts with 5 inch fused silica square plates
coated with a thin film of chromium and a resist. The resist is
exposed with an optical pattern generator, in case of a
photoresist, or with an electron beam lithography tool, in case of
an electron-beam resist (e.g. PMMA). The resist is then developed
and the chromium etched ["Microsystem design", S. Senturia, 2001,
pages 50-57]. COG photomask repair technology thus focuses on the
deposition of opaque patches in the location of clear defects and
the removal of chromium left in unwanted areas.
[0020] Phase shifting masks (PSM) take advantage of destructive
interference at pattern edges to improve contrast. Alternating
Aperture PSMs, also called strong-shifters are fabricated by
etching 180.degree.-phase-shifting windows in alternating clear
areas of the quartz mask. Repair technologies in this area focus on
substrate defects (quartz bumps and divots) ["Alternating phase
shift mask defect printability for 130 nm and 100 nm KrF
lithography", Kim et al., International SEMATECH, May 19,
2000].
[0021] Attenuating PSM (weak-shifters) relies on the deposition of
a partially transmitting, 180.degree.-phase-shifting material (e.g.
molybdenum silicide). Light diffracted from a clear opening in the
photomask will destructively interfere with light from the
phase-shifted areas, improving contrast. Additive repair of such
photomask relies on the deposition of a layer with similar overall
optical properties (transparency, index of refraction), which may
be achieved by precise control of the chemistry and the thickness
of the patch.
[0022] Newer lithographies increasingly can be considered to be
nanolithography as opposed to microlithography and may combine 193
nm and 157 nm technologies and what is called Next Generation
Lithographies (NGL), the primary contenders including Extreme UV
(EUV, 14.6 nm), electron projection lithography (EPL), including
SCAPEL, and X-ray lithography. EUV masks will likely consist of
diffractive reflectors containing as many as 40 layers (e.g.
Mo/Si). This makes defect inspection and repair absolutely
critical. Also, in contrast with photomasks, which have a 4:1 or
5:1 mask-to-wafer ratio, NGL masks are often 1:1. A high-precision
tool, capable of nanometer-scale XY control and able to process
multiple layers with high Z resolution is therefore required for
the fabrication and repair of masks for emerging lithographies.
Microfabrication, Vol. I, by Peckerar et al. "Issues in
Nanolithography for Quantum Effect Device Manufacture (pages
681-763) discloses Proximal Probe Electron Lithography (pages
710-716), which is hereby incorporated by reference.
[0023] A need exists for facile, rapid, versatile, and
cost-effective methods to fabricate, enhance, and repair mask,
photomasks, and similar structures having defects and holes,
particularly at nanoscopic dimensions, and particularly in additive
mode wherein very small amounts of material are added to effect
repair. A further need exists for these methods to be compatible
with existing and newer photomask technologies.
SUMMARY
[0024] In this section, the invention is summarized, although this
summary should not limit the invention which is described in detail
and claimed below.
[0025] The invention provides a method for additive repair in the
semiconductor industry with fine control over lateral dimensions
and height comprising: depositing material to a defective mask by
direct write nanolithography from a tip for additive repair.
[0026] The invention also provides a method for nanolithography
comprising: (1) providing a mask, (2) providing a scanning probe
microscope tip, wherein the tip is coated with a patterning
compound, (3) contacting the coated tip with the mask so that the
compound is applied to the mask.
[0027] The invention also provides a method for nanolithography
comprising: (1) providing a substrate having at least one defect,
(2) providing a tip with a patterning compound, (3) using the tip
with the substrate so that the compound is applied to the substrate
at the defect to repair the defect.
[0028] The invention also provides a method for mask fabrication
comprising adding material to a substrate to form a mask by direct
write nanolithography with use of a scanning probe microscopic tip
to pattern material on the substrate.
[0029] The invention also provides a method of nanolithography
comprising using a tip to layer one or more patterning compounds on
a substrate so the one or more patterning compounds form a
structure at least about 10 nm high. The structure can be a mask
enhancement structure.
[0030] The invention also provides a method for nanolithography
comprising using a coated atomic force microscope tip to deposit a
patterning compound on a substrate in mask fabrication.
[0031] The invention also encompasses masks repaired, enhance, and
fabricated by these methods. The invention also provides methods of
using scanning probe microscopy to repair and fabricate masks by
additive repair and additive lithography, respectively.
[0032] Another aspect of the invention is a repaired photomask
comprising a defective mask substrate comprising at least one
nanometer-scale opening which is a defect, and at least one
additive repair nanostructure at least partially filling the
opening. The nanostructure can also substantially fill the
opening.
[0033] The present invention also provides (i) engineered
nanometer-scale deposits placed with nanometer-scale accuracy; and
in particular (ii) engineered nanometer-scale etched openings (as
disclosed herein) and similar objects; (iii) engineered
nanometer-scale filled openings and similar objects; (iv)
structures or assemblies containing such objects; (v) methods for
preparing (etching/depositing/filling) and using nanometer-scale
deposits and their assemblies, alone or in combination with other
objects; (vi) apparatus to fabricate such objects.
[0034] More specifically, the following articles and methods are
part of the invention: (vii) nanometer-scale deposits or openings
etched or filled by a process that utilizes a direct write
deposition nanolithography technique, and in particular (viii)
nanometer-scale deposits formed (or openings etched or filled) by
direct write, Dip Pen.TM. Nanolithographic printing and deposition
(DPN.TM.); (ix) methods of fabricating such features, including (x)
pre-nanolithography treatments (e.g. solvent or plasma cleaning,
adhesion layer deposition), (xi) nanolithography methodology
(including ink composition and its delivery to the probe), and
(xii) post-nanolithography processes (e.g. reduction, thermal
treatment, curing . . . ); each treatment being applied in-situ or
ex-situ, once or multiple times, with or without repetition; as
well as (xiii) the apparatus(es) to do so.
[0035] Examples include but are not limited to (xiv) the deposition
of and/or filling with e.g. with (a) a metal-rich material, such a
metal or an alloy, and precursors thereof; (b) a carbon-rich
material, such as graphite-like carbon (including fullerenes and
carbon nanotubes and carbon nanotube derivatives), and diamond-like
carbon; (c) colloidal particles, including metallic ones; and
mixtures containing thereof, (d) one or more high-molecular-weight
compound(s), including organic and inorganic polymers, with or
without the addition of colloidal particles; (xv) the deposition of
metal oxides, glasses, silicates and related materials; (xvi) the
sequential deposition/filling of materials according to xiv) and
xv) (multilayer formation) with, optionally, control of the
thickness and roughness of each layer, as well as the edge
geometry.
[0036] Practical applications include (xvii) the filling of a
nanometer-scale opening of a feature with a material having similar
optical properties (including index of refraction, absorbance, and
reflectivity) to the surroundings of the openings, including
(xviii) the filling of a nanometer-scale opening with or
nanometer-scale deposition of a material opaque to electromagnetic
radiation, including visible and UV light, and/or charged
particles; and in particular (xix) the repair of defects in
microfabricated structures and their assemblies; (xx) the repair of
defects present in optical lithography photomasks and (xxi) in
microelectronic chips and microelectromechanical systems
(MEMS).
[0037] Other aspects of this disclosure include, for example:
[0038] (xxii) the methods that associate the articles and methods
described above with (a) other substrate modification methods, in
particular (b) other photomask repair methods, including (c)
subtractive repair methods capable of removing features by
(electro)chemical etching, mechanical removal, local heating, laser
ablation/evaporation, ion etching or a combination thereof; in
particular (d) subtractive nanomachining processes; and (e)
subtractive nanomachining processes, in which the removal is
assisted by the deposition of a lubricant or etchant esp. using
DPN.TM. printing as the source;
[0039] (xxiii) the apparatus implementing the above methods; (xxiv)
the combination of the methods or apparatus described above and of
methods or apparatus designed to detect defects and their influence
on wafer printing. The latter includes methods and apparatus based
upon the principles of optical microscopy (including stepper
equivalents) and scanning probe microscopy, including SPM of a
large area via a large array of probes.
[0040] DPN.TM. printing--and deposition-based processes may also be
used for (xxv) contamination control by local delivery of a
cleaning agent or solvent, or by combination of mild mechanical
removal and reagent deposition.
[0041] It is another object of the invention to provide methods
(xxvi) to enhance a mask made by conventional methods with features
otherwise difficult to fabricate, for example ( xxvii) to add OPC
(optical phase correction) features. It is known that image
fidelity issues with optical pattern generators limit their
usefulness for the patterning of high-density features and
sub-resolution OPC features, such as scattering bars. DPN.TM.
patterning with parallel probe arrays may compete effectively with
e-beam direct writing, in term of overall costs and throughput, for
the fabrication of wavefront engineering features, such as OPC and
PSM features.
[0042] It is another object of the present invention (xxviii) to
provide DPN.TM. printing-and deposition-based methods and apparatus
suitable as the principal technology to pattern photomask wafers,
including through the use of high-throughput probe arrays. Among
key advantages of DPN.TM. printing and deposition is its ability to
fabricate nanostructures, such as networks of nanodots or lines,
within micron-scale areas (e.g. the mask patterns), giving the mask
designer access to the unique optical properties of low-dimensional
systems.
[0043] Other applications include but are not limited to (xxix) the
modification of magnetic read/write heads for hard drives; and
(xxx) the fabrication or modification of probes, such as scanning
probe microscopy/lithography probes, DPN.TM. printing and
deposition probe or probe arrays;
[0044] Advancing these technologies requires the development of
(xxxi) novel probe geometries, (xxxii) novel probe
positioning/actuation technologies, (xxxiii) novel probe arraying
and multiplexing technologies; (xxxiv) novel methods of ink
delivery to the probe, as well as (xxxv) methods to assess the
suitability of fabricated patterns, e.g. their mechanical and
chemical performances and their stability in following processing
steps.
BRIEF DESCRIPTION OF THE DRAWINGS
[0045] FIG. 1 illustrates different types of mask defects and
additive and subtractive repairs.
[0046] FIG. 2 illustrates repair of defects including location of
the defect and ink deposition steps.
[0047] FIGS. 3A and 3B illustrate additive and subtractive
repair.
[0048] FIG. 4 illustrates metal patterning.
[0049] FIG. 5 illustrates metal/metal oxide patterning.
[0050] FIG. 6 illustrates metal patterning.
[0051] FIG. 7 illustrates particulate patterning.
[0052] FIG. 8 illustrates colloidal patterning.
[0053] FIG. 9 illustrates polymeric precursor patterning.
[0054] FIG. 10 shows palladium patterning.
[0055] FIG. 11 shows palladium patterning.
[0056] FIG. 12 shows metal patterning.
[0057] FIG. 13 illustrates a schematic of the mask repair
process.
[0058] FIGS. 14A and 14B illustrate multilayered patterning.
[0059] FIG. 15 shows defective mask structures.
[0060] FIG. 16 shows defective mask structures (closer view).
[0061] FIG. 17 shows initial additive repair (dots).
[0062] FIG. 18 shows initial additive repair, with a high dot.
[0063] FIG. 19 shows initial additive repair (lines).
[0064] FIG. 20 shows defective mask structure with nanoscale
hole.
[0065] FIG. 21 shows initial additive repair.
[0066] FIG. 22 shows additive repair.
[0067] FIG. 23 shows multilayering repair.
[0068] FIG. 24 illustrates elastomer tip modification.
[0069] FIG. 25 shows elastomer modified tips.
[0070] FIG. 26 illustrates an embodiment with two chemically
reactive inks.
[0071] FIG. 27 illustrates local curing by irradiation from an NSOM
tip.
DETAILED DESCRIPTION
[0072] This application claims priority benefit to provisional
application 60/419,781 filed Oct. 21, 2002 to Crocker et al.
("Nanometer-scale engineered structures, methods and apparatus for
fabrication thereof, and applications to photomask repair and
enhancement"), which is hereby incorporated by reference in its
entirety. The references cited in the introduction section can be
referred to in the practice of the present invention. No admission
is made that any reference cited in this patent application,
including in the introduction section, is prior art.
[0073] I. Direct Write Nanolithography and Use of Tips
[0074] The present invention provides nanometer-scale functional
features (including deposits, filled openings, and etched
openings), as well as the enabling methods and apparatus. Examples
of specific features to be fabricated and repaired include:
[0075] (a) Defect repair patches in transmission photomasks and
reflection photomasks such as these used for extreme UV
lithography; this includes the deposition of opaque or transparent
materials, or their etching.
[0076] (b) Vias, lines and defect thereof, in microelectronic
circuits, the application being the repair of high-value chips;
[0077] (c) Filled defects in microelectromechanical systems (MEMS),
the application being the repair, modification or testing of
prototypes.
[0078] The present invention also provides the methods and
apparatus (a) for the modification of existing photomasks, as a
corrective measure or as an enhancement measure; (b) for the
fabrication of photomasks;
[0079] Dip Pen.TM. Nanolithographic printing and deposition
(DPN.TM. printing and deposition) can be used in conjunction with
novel inks, probes, pre-/post-deposition and ink delivery methods.
DPN.TM. printing and deposition, built upon the technique of Atomic
Force Microscopy (AFM) allows the deposition of one or more inks
with nanometer scale precision, enabling the fabrication, on a
variety of surfaces, of insulator, semiconductor, and metallic
nanostructures with tailorable physical properties and fine control
over lateral dimensions (several nanometers to many microns) and
height (angstroms to hundreds of nanometers).
[0080] Specifically, the following attributes position DPN.TM.
printing as a powerful technique for a new additive mask repair and
fabrication technique at unprecedented resolution:
[0081] 1. High resolution. By optimizing particular ink/substrate
combinations feature sizes as small as 12 nm with spatial
resolution of .about.5 nm can be achieved.
[0082] 2. Works in ambient environment DPN.TM. printing and
deposition utilizes ink transport from a coated probe to a
substrate in ambient environment conditions of temperature,
pressure and humidity. In general, there is no need for high vacuum
conditions.
[0083] 3. Direct writing. No resists are needed and the molecules
of interest can be placed exactly (and only) where desired, thereby
minimizing contamination and alteration of the rest of the
substrate. This ability also allows in situ deposition of multiple
inks on a substrate.
[0084] Chemical generality. DPN.TM. printing and deposition to
pattern inks can be used with compounds ranging from simple organic
molecules (such as alkanethiols) to oxides and metals and
nanoparticles on surfaces ranging from gold to oxides to
semiconductors.
[0085] The present invention consists essentially of these and
other basic and novel features.
[0086] DPN.TM. printing and deposition methods are extensively
described in the following patent applications and patent
publications, which are hereby incorporated by reference in their
entirety, particularly with respect to the experimental parameters
for carrying out the deposition:
[0087] 1. U.S. Provisional application 60/115,133 filed Jan. 7,
1999 ("Dip Pen Nanolithography").
[0088] 2. U.S. Provisional application 60/157,633 filed Oct. 4,
1999 ("Methods Utilizing Scanning Probe Microscope Tips and
Products Therefor or Produced Thereby").
[0089] 3. U.S. Regular patent application Ser. No. 09/477,997 filed
Jan. 5, 2000 ("Methods Utilizing Scanning Probe Microscope Tips and
Products Therefor or Produced Thereby").
[0090] 4. U.S. Provisional application 60/207,713 filed May 26,
2000 ("Methods Utilizing Scanning Probe Microscope Tips and
Products Therefor or Produced Thereby").
[0091] 5. U.S. Provisional application 60/207,711 filed May 26,
2000 ("Methods Utilizing Scanning Probe Microscope Tips and
Products Therefor or Produced Thereby").
[0092] 6. U.S. Regular application Ser. No. 09/866,533 filed May
24, 2001 ("Methods Utilizing Scanning Probe Microscope Tips and
Products Therefor or Produced Thereby").
[0093] 7. U.S. patent publication number 2002/0063212 A1 published
May 30, 2002 ("Methods Utilizing Scanning Probe Microscope Tips and
Products Therefor or Produced Thereby").
[0094] 8. U.S. patent publication number 2002/0122873 A1 published
Sep. 5, 2002 ("Nanolithography Methods and Products Produced
Therefor and Produced Thereby").
[0095] 9. PCT publication number WO 00/41213 A1 published Jul. 13,
2000 based on PCT application no. PCT/US00/00319 filed Jan. 7, 2000
("Methods Utilizing Scanning Probe Microscope Tips and Products
Therefor or Produced Thereby").
[0096] 10. PCT publication number WO 01/91855 A1 published Dec. 6,
2001 based on PCT application no. PCT/US01/17067 filed May 25, 2001
("Methods Utilizing Scanning Probe Microscope Tips and Products
Therefor or Produced Thereby").
[0097] 11. U.S. Provisional application 60/326,767 filed Oct. 2,
2001, ("Protein Arrays with Nanoscopic Features Generated by
Dip-Pen Nanolithography").
[0098] 12. U.S. Provisional application 60/337,598 filed Nov. 30,
2001, ("Patterning of Nucleic Acids by Dip-Pen
Nanolithography").
[0099] 13. U.S. Provisional application 60/341,614 filed Dec. 17,
2001, ("Patterning of Solid State Features by Dip-Pen
Nanolithography").
[0100] 14. U.S. Provisional application 60/367,514 filed Mar. 27,
2002, ("Method and Apparatus for Aligning Patterns on a
Substrate").
[0101] 15. U.S. Provisional application 60/379,755 filed May 14,
2002, ("Nanolithographic Calibration Methods").
[0102] 16. U.S. Regular application Ser. No. 10/647,430 filed Aug.
26, 2003 (attny docket no. 083847-0200) ("Processes for Fabricating
Conductive Patterns Using Nanolithography as a Patterning Tool")
describes conductive compositions and patterning thereof.
[0103] 17. U.S. Provisional Application 60/425,252 filed Nov. 12,
2003 ("Methods and Apparatus for Ink Delivery to Nanolithographic
Probe Systems") to Cruchon-Dupeyrat et al.
[0104] Another illustration of the DPN methods can be found in the
patent publication, 2003/0022470 to Chang Liu et al. published Jan.
30, 2003 ("Parallel, Individually Addressable Probes for
Nanolithography"), which is hereby incorporated by reference.
[0105] DPN.TM. printing and deposition-related products, including
hardware, software, and instrumentation are also available from
Nanolnk, Inc. (Chicago, Ill.).
[0106] II. Mask Repair and Fabrication
[0107] Mask fabrication and repair is disclosed in the following
patents, which are hereby incorporated by reference in their
entirety, particularly for their disclosure on the materials of the
photomask and repair: U.S. Pat. No. 6,090,507 to Grenon et al.
(Jul. 18, 2000); U.S. Pat. No. 6,165,649 to Grenon et al. (Dec. 26,
2000); U.S. Pat. No. 6,373,976 to Pierrat et al. (Apr. 16, 2002);
U.S. Pat. No. 6,139,993 to Lee et al. (Oct. 31, 2000); 4,727,234 to
Oprysko et al. (Feb. 23, 1988); U.S. Pat. No. 6,096,459 to Yang
(Aug. 1, 2000); U.S. Pat. No. 6,114,073 to Yang (Sep. 5, 2000);
U.S. Pat. No. 4,200,668 to Segal et al. (Apr. 29, 1980); and U.S.
Pat. No. 6,353,219 to Kley (Mar. 5, 2002).
[0108] In addition, U.S. Pat. No. 6,451,375 to Cotte et al. (Sep.
17, 2002) is incorporated by reference in its entirety,
particularly for its disclosure on depositing films on nanometer
structures using supercritical fluid technology.
[0109] Also, U.S. Pat. No. 4,160,049 to Narcus (Jul. 3, 1979) is
incorporated by reference in its entirety, particularly for its
disclosure on electroless deposition of nickel coatings.
[0110] In addition, the following text is incorporated by reference
in its entirety: Handbook of Microlithography, Micromachining, and
Microfabrication, Vol. I and II, including Vol. I, Chapter 5
"Photomask Fabrication Procedures and Limitations" by Skinner et
al. (pages 377-474), particularly for its discussion of substrate
preparation, pattern writing, pattern processing, metrology,
inspection for pattern integrity, cleaning, repair, pellicle
attachment, final defect inspection, and materials. Also, Chapter 8
of this book written by Peckerar et al., discussed above, is
incorporated by reference in its entirety, particularly for its
disclosure about proximal probe lithography.
[0111] Repairing defects in masks and reticles is also disclosed in
Silicon Processing for the VLSI Era Vol. I: Process Technology,
pgs. 485-486, Wolf and Tauber, 1986, which is hereby incorporated
by reference in its entirety.
[0112] For advanced mask repair, the following references can be
used: "Issues for advanced reticle fabrication: (You Want that
reticle when?)", J. G. Maltabes, Future Fab., Vol. 11, June
29.sup.th, 2001.
[0113] FIG. 1 provides a schematic diagram of common mask defects,
including photomask defects, before (left-hand side) and after
repair (right-hand side): (1) thinned line or edge notch; (2)
pin-hole defect; (3) gap; (4) spike or protuberance; (5) bridge or
neck; (6) corner defect; (7) bump or divot in the (quartz)
substrate; (8) spurious opaque spot. Clear defects may be repaired
by an additive process, such as deposition of an ink (top), while
opaque defects may be removed by a subtractive process (bottom),
for example, the deposition of a chemical etchant, assisted or not
by mechanical action.
[0114] A defect can be a flaw, an imperfection and/or a weakness.
It refers for example to:
[0115] a--an unwanted opening (as defined above) within an
engineered feature;
[0116] b--an unwanted spot, protuberance or spike;
[0117] c--a bridge or neck between two engineered features;
[0118] d--an anomaly of the thickness of the substrate or its
light-propagating properties;
[0119] For purposes of this disclosure, a nanometer-scale feature
can be an object, one dimension of which (at least) is (a) less
than a few micrometers but more than 500 nm (nanometers); (b) less
than 500 nm but more than 100 nm; (c) less than 100 nm but more
than 10 nm; or (d) less than 10 nm down to molecular
dimensions.
[0120] Moreover, an opening can be (1) an area where something is
missing; (2) a hollow between ridges or protuberances. It can
include, but is not limited to: (a) a hole, perforation or
aperture; (b) a gap; (c) a recess, indentation or cavity; (d) a
fissure, crack or break.
[0121] In this invention, the partial or substantially complete
fillings of openings having a lateral dimension of about 100 nm or
less, about 80 nm or less, about 56 nm, or less, or about 35 nm or
less, are particularly preferred, based on projected semiconductor
nodes.
[0122] III. FIGS. 2 and 3A and FIG. 3B
[0123] FIG. 2 gives examples of a few typical process sequences
e.g. for an additive (deposition) repair process. Examples of
additive mask repair procedures. (a) The initial defect is located
either by means of an external instrument (e.g. aerial imager)
and/or by scanning the probe to obtain a scanning probe microscopy
image; (b) Ink is deposited in the defect area under manual or
automatic guidance until completion, as shown in (c); if necessary,
a post-nanolithography treatment is applied; e.g., to trigger the
physical or chemical transformation of the deposit (curing); It
might include (d1) heating the wafer; (d2) irradiating it with
electromagnetic radiation (e.g., UV light), or (d3) soaking it in
an appropriate solution, e.g. a reducing agent in an aqueous or
organic solvent, or (d4) exposing it to a chemical vapor (e.g., a
reducing agent, a base, or the like), not depicted in FIG. 2. Steps
d1 to d3 may be applied to the whole wafer or locally to the
vicinity of the pattern. (e) Once the repair is completed, the
wafer is optionally cleaned (for example, to remove residual inks)
and the repaired defect optionally inspected using atomic force
microscopy (AFM) or aerial imaging metrology.
[0124] FIG. 3 provides an additional schematic diagram of a
possible additive/subtractive photomask-repair apparatus. It is
possible to simultaneously or sequentially repair both clear and
opaque defects with the same instrument in the same session, if
combining DPN.TM. printing technology with nanomachining and/or
DPN.TM. printing-assisted nanomachining. An array of two active
microfabricated cantilevers is brought in close proximity with the
photomask wafer (1), for example by monitoring the cantilever
deflection during approach. The defect (2) to repair is located
e.g. by a combination of actinic optical microscopy and low-force,
high-speed SPM imaging of the wafer associated with pattern
recognition software. The left probe (3) is supplied with and
coated with an ink, while the right one, a high-force-constant
cantilever, capable of applying high contact force and/or
delivering a second ink can and can serve as a nanomilling tool.
The cantilevers can be individually actuated, e.g. by the thermal
expansion of a bimorph formed by a metallic heater on the back of
the cantilever and the structural material of the cantilever
itself. In the additive repair mode [A], probe 3 is brought in
contact with the substrate and rastered at slow speeds to fill the
clear defect area. In the subtractive repair mode [B], probe 4
applies a large force to areas where spurious metal has been
deposited in order to scrape it. Or probe 4 can remove spurious
metal by rastering multiple times the area to scrape it. The probe
4 may be optionally coated with an ink (5) that serves as a
lubricant and/or etchant during nanofabrication and nanomachining
(hence, it can be a DPN.TM. printing-assisted nanomachining).
[0125] In particular, in one embodiment, the apparatus disclosed in
U.S. Pat. No. 6,353,219 to Kley can be adapted to operate in a
direct-write nanolithographic printing or deposition mode to make
and repair photomasks, particularly, by adding materials, with use
of scanning probe microscopic tips coated with one or more inks, as
disclosed herein.
[0126] IV. Patterning Compounds and Deposit Materials
[0127] In addition, a deposit can be the result of one or multiple
steps of deposition nanolithography (including but not limited to
Dip Pen.TM. Nanolithographic printing and deposition processes, and
related processes), optionally followed or preceded by additional
processing steps. It can be, for example, a dot or a line deposited
on top of a substrate or any pattern formed by combinations of dots
and lines. It can also fill a defect or an engineered recess.
[0128] For purposes of the present disclosure, an ink or patterning
compound can be one or a plurality of chemical compounds to be
delivered in a controlled manner at the nanometer scale. Inks may
be fluids, gases, solid matters, or composition thereof. They may
be monophasic or multiphasic, homogeneous or heterogeneous in
nature, and may include solvents, tensioactive compounds and other
adjuvants.
[0129] Examples of inks or patterning compounds include:
[0130] (1) Small organic molecules, and specifically molecules
capable of forming self-assembled monolayers, including thiols,
silanes, and metal bisphosphonate derivatives;
[0131] (2) Organometallic and inorganic compounds, including metal
salts, metal complexes, including these of nickel, chromium,
platinum, palladium, copper, gold, silver, iron, molybdenum and
tungsten,
[0132] (3) Reducing or oxidizing agents, including borohydrides
(e.g. NaBH4), aluminum and tin compounds, such as lithium
tetrahydridoaluminate (lithium aluminum hydride), ethylene diamine,
borane complexes (dimethylamine:borane), ethylene glycol, PEG, and
on the other hand, and peroxides;
[0133] (4) Solution and suspension of nanoparticles, including
metallic clusters and polymeric particles, such as gold and silver
colloids, latex spheres and derivatives thereof, and MoSi.sub.2
powders;
[0134] (5) Polymeric compounds; or precursors to polymeric
compounds such as, for example, formaldehyde and resorcinol;
[0135] (6) Materials of interest in microelectronics processing,
including photolithographic resists, strippers, and etchants;
[0136] (7) Electroless deposition and electroplating solutions;
[0137] (8) Catalysts;
[0138] (9) Photographic ink formulations, including silver salt
emulsions;
[0139] (10) Photosensitizing dyes or plasticizers (ethylcarbazole)
as well as solutions, dispersions and mixtures thereof;
[0140] Specifically, the chemical compounds listed below and the
mixtures thereof can be used as inks or patterning compounds:
[0141] (a) copper formate or acetate, silver sulfate, silver
nitrate, silver tetrafluroborate, palladium chloride, acetate, and
acetylacetonate, hexachloroplatinic(IV) acid, ammonium iron
citrate
[0142] (b) carboxylates, (pseudo-)halides, sulfates, and nitrates
of zinc, nickel, cadmium, titanium, cobalt, lead iron, and tin;
[0143] (c) metalcarbonyl complexes, including chromium
hexacarbonyl,
[0144] (d) amine bases, including cyclohexylamine, 3-picoline,
(iso)quinoline, cyclopentylamine, dimethylsulfoxide,
dimethylformamide, formamide, ethylene diamine
[0145] (e) polymers, including poly(ethyleneoxide),
poly(methylmethacrylate), poly(vinylcarbozol), poly(acrylamide)
[0146] Also included are compounds and mixtures thereof, which,
after processing, respectively yield optically opaque and optically
transparent materials, respectively, at the wavelength of
lithography, including the following:
[0147] a--metals, such as chromium, palladium, platinum, iron,
molybdenum, nickel, silver, and tungsten; or
[0148] b--materials primarily composed of silica, silicates,
alumina, molybdenum silicide, as well as sol-gel precursors,
orthosilicates/borates/aluminates and/or metal oxides, such as
In.sub.2O.sub.3 and SnO.sub.2, MoSi (e.g. spin-on glasses,
ITO);
[0149] Deposition steps include but are not limited to the
deposition of one or more inks e.g. by DPN.TM. printing or
deposition with one or more probe(s). Possible inks include but are
not limited to precursors, compounds that will form the bulk of the
final pattern, catalysts, solvents, small molecule or polymeric
carrier agents, host matrix materials, or sacrificial reducing
agents, and mixtures of above materials. They may be deposited as
thin films or as thick multilayers (formed by multiple deposition
steps), with or without variation of the chemical composition from
layer to layer.
[0150] Additional embodiments are shown in FIGS. 26 and 27. FIG. 26
shows use of a plurality of inks which react with each other. FIG.
27 shows use of external radiation to induce local cure of the ink.
Additional embodiments are described in the figures and
examples.
[0151] V. Pre-Deposition and Post-Deposition Steps
[0152] In principal, deposition and etching methods considered in
this invention also consist essentially of
[0153] (a) zero or more pre-deposition steps, including zero or
more defect characterization steps;
[0154] (b) zero or more probe/substrate cleaning or chemical
modification steps aimed at improving ink coating;
[0155] (c) one or more deposition steps, which may use dip pen
nanolithography technology;
[0156] (d) zero or more post-deposition steps, including zero or
more cleaning steps;
[0157] (e) zero or more inspection steps;
[0158] Pre-deposition substrate surface treatment steps include but
are not limited to (in no particular order):
[0159] (a) plasma, UV, or ozone cleaning, washing, drying,
blow-drying,
[0160] (b) chemical cleaning, such as piranha cleaning, basic
etching (e.g. hydrogen peroxide and ammonium hydroxide)
[0161] (c) chemical or physical modification of the substrate to
promote ink transport, or adhesion, or covalent modification (e.g.,
base treatment to impart a charged surface on silicon oxide,
silanization with amino- or mercapto-silanizing agents, polymers
carrying chemically reactive functional groups)
[0162] (d) protection against side-effects of following process
steps (e.g. coating with a resist or thin film),
[0163] (e) inspection of the substrate with techniques derived from
optical microscopy (e.g. AIMS), electron microscopy (e.g. CD SEM)
or imaging (e.g. EDS, AES, XPS), ion imaging (e.g. TOF SSIMS) or
scanning probe imaging (e.g. AFM, AC AFM, NSOM, EFM . . . ),
[0164] (f) any of the steps detailed below in the post-deposition
section, and combination thereof,
[0165] Probe cleaning or modification steps include but are not
limited to (in no particular order):
[0166] (a) plasma cleaning, washing, drying, blow-drying,
[0167] (b) chemical cleaning, such as piranha cleaning, basic
etching (eg. hydrogen peroxide and ammonium hydroxide), and sodium
hydroxide;
[0168] (c) chemical or physical modification of the probe to
promote or enhance ink coating, adhesion, or transport (eg. base
treatment to impart a charged surface of the silicon nitride tip,
silanization with amino- or mercapto-silanizing agents,
non-covalent modification with small molecule or polymeric agents
such as poly(ethyleneglycol)) Such modifications include those that
increase loading of the ink on the tip by increasing porosity or
enhancing surface area available for ink delivery.
[0169] Post-deposition steps include but are not limited to (in no
particular order):
[0170] (a) Heating of the substrate, for example with a heat lamp,
hot air blower, or hot plate, or furnace;
[0171] (b) Irradiation of the substrate with electromagnetic
radiation (esp. IR, visible, and UV light) or charged particles
(e.g. electrons, ions drawn from a gun or a plasma source). This
process may occur in air, vacuum, or in solution, with or without
photosensitizing agents,
[0172] (c) Immersion of the patterned substrate in one or more
solutions,
[0173] (d) Electrochemical reduction,
[0174] (e) Chemical reduction,
[0175] (f) Exposure of the patterned substrate to a vapor or
gas,
[0176] (g) Sonication of the patterned substrate, as well as all
nano-scale, local equivalents of the steps outlined above, if
applicable, the source of the energy and/or composition of matter
been provided by one or more probe(s), which may or may not be the
same than the DPN probe(s); which include but is not limited
to:
[0177] (h) Local heating of the deposited matter or surrounding
substrate,
[0178] (i) Local irradiation of the deposited matter or surrounding
substrate, and all combinations thereof.
[0179] The succession of all or some steps may be repeated several
times.
[0180] A series of additional embodiments, including some working
examples, are described further below.
[0181] Part 1: Direct Deposition
[0182] In a first embodiment of the invention, one or more ink(s)
is (are) deposited in the area with e.g. Dip Pen.TM.
Nanolithographic printing or deposition. Ink with different
chemical compositions may be deposited in succession. For example,
a priming ink may be deposited first to afford appropriate surface
chemistry. A second ink is then deposited one or multiple times by
multiple repetition of the deposition step, layer by layer, until a
sufficient thickness is achieved.
[0183] FIG. 6 illustrates stepwise deposition of metal precursor
inks in the form of nanometer thick layers. Each layer may or may
not be treated with chemical reducing agents or radiation prior to
application of subsequent layers. An appropriate number of layers
are deposited to form optically opaque structures of metal, metal
oxide, or other opaque materials.
[0184] FIG. 26 represents another embodiment.
EXAMPLE 1
[0185] A polymer or polymer precursor is deposited and air-dried or
air-cured. To obtain optically adequate (i.e. opaque) deposits, the
curable polymer/precursor may be mixed with a colloidal solution,
esp. metallic or metal oxide nanoparticles. Commercially available
inks include water-, methylisobutyl ketone or isopropanol-based
silver and carbon nanoparticle paints, such as these commercialized
by Ted Pella, Inc.
EXAMPLE 2
[0186] A priming layer, such as .omega.-functionalized
self-assembled monolayer (e.g. trialkoxy- or trichlorosilanes on
quartz, alkanethiols on coinage metals) is deposited on the
substrate. The .omega.-terminal functional group (e.g. --SH,
--COOH, --CHO . . . ) is selected as a function of the subsequent
inks to deposit. For example, ligand-protected metallic colloids
(gold, silver) may adhere by place-exchange between the ligand and
the layer terminal group, and by electrostatic interaction. In
another example, a (e.g., amine-rich or carboxylic acid-rich)
polyelectrolyte is deposited that has an opposite charge to that of
the .omega.-terminal group. Charged colloidal particles may then be
deposited to form an electrostatic sandwich, as described by Chen
et al [K. M. Chen, X. Jiang, L. C. Kimerling and P. T. Hammond,
"Selective Self Organization of Colloids on Patterned
Polyelectrolyte Templates", Langmuir, 16, 7825-7834 (2000).] and by
Wuelfing et al (Chem. Mater. 2001, 13, 87-95)
[0187] Part 2: Deposition and Application of a Chemical Compound Or
Mixture
[0188] In a second embodiment of the invention, deposition is
preceded or followed by application of one or more compound(s) or
mixture(s) to the whole substrate. in a preferred embodiment, the
substrate is immersed in one or more bath(s) after deposition of
one or more ink(s) e.g. by DPN.TM. printing or deposition. the
process may be repeated multiple times. for example, the precursor
may be a (noble metal) catalyst and the bath an electroless
deposition solution, or the precursor may be a metallic salt and
the bath a reducing agent.
EXAMPLE 3
Metal Deposition and Chemical Reduction
[0189] Palladium chloride (PdCl.sub.2) or acetate was deposited
from an aqueous solution by DPN.TM. printing or deposition in the
area to fill with metal. the palladium salt structures were reduced
to the metallic state, Pd.degree., by deposition of a reducing
agent (e.g. stannous chloride (SnCl.sub.2), aqueous
dimethylamine-borane, dimethylsulfide:borane, or sodium
borohydride) by DPN.TM. printing or deposition, or flooding, or
immersion of the substrate in a bath containing a solution of the
reducing agent. This procedure may also be used to deposit other
metals, such as silver, copper, iron, platinum, gold, and cobalt
when the appropriate metal salt is chosen as an ink.
[0190] FIG. 10. (Working Example) AFM images before and after the
reduction reaction are shown in FIG. 10. Deposition of disodium
palladium chloride (1 mg/.mu.L in water) with 10% polyethyleneoxide
(MW 10,000) via DPN.TM. printing on amino-silanized glass (Schott
Glass company), and subsequent chemical reduction to palladium
metal using 0.03 M aqueous solution of dimethylamine:borane complex
(DMAB). Atomic force micrographs of pattern showed (a) pallidium
salt pattern before reduction, (b) metal line and dot pattern after
reduction by DMAB, and (c) a line scan indicating the height of the
dot patterns.
EXAMPLE 4
Metal Deposition Using Electroless Deposition
[0191] Sodium tetrachloropalladate II (Palladium chloride,
NaPdCl.sub.4) or acetate is deposited from an aqueous solution by
DPN in the area to fill with metal. the palladium is reduced to the
catalytic state, Pd.degree., by deposition of a reducing agent
(e.g. stannous chloride (SnCl.sub.2), dimethylamine-borane or
sodium borohydride) by DPN.TM. printing or other deposition method
or immersion in a bath. the palladium features are then put in
contact with an electroless deposition bath, including the
following examples:
[0192] (1) nickel sulfate, sodium hypophosphite, lactic acid,
sodium hydroxide, thiourea (nickel deposit);
[0193] (2) nickel sulfate, sodium hypophosphite and chloride,
sodium succinate, hydrochloric acid (nickel deposit);
[0194] (3) cobalt chloride, sodium citrate, ammonium chloride
(cobalt deposit);
[0195] (4) copper sulfate, sodium hydroxide, formic acid, EDTA,
methyldichlorosilane (copper deposit);
[0196] (5) potassium gold cyanide, potassium cyanide and hydroxide,
potassium borohydride (gold deposit);
[0197] (6) palladium chloride, hydrochloric acid, ammonium
hydroxide and chloride, sodium phosphate monobasic (palladium
deposit);
[0198] (7) silver and sodium cyanide, sodium cyanide and hydroxide,
dimethylamine-borane (silver deposit);
[0199] (8) stannic chloride (SnCl.sub.4), chromium(III) oxide
(Cr.sub.2O.sub.3) and NH.sub.4F.sub.2 (chromium deposit). See also
"electroless rhodium plating" [Kozlov et al., U.S. Pat. No.
6,455,175, 2002], which is hereby incorporated by reference. a
composite film may be deposited, using an electroless deposition
solution containing colloidal particles. Platinum salts have also
been used in this procedure to form platinum metal structures which
catalyze metallic cobalt deposition. Immersion deposition, which
uses the substrate or a sacrificial layer on the substrate as the
oxidized species, is also an option.
EXAMPLE 5
[0200] a polymer catalyst is deposited on the substrate and put in
presence of a precursor solution (monomer). the reaction of a gas
or liquid at the catalyst forms surface-bound polymer brushes,
which can then be pyrolyzed or metalized via electroless
deposition. Generally, methods are desired for depositing polymers
and then pyrolyzing them into a chemically resistant and opaque
carbon-rich residue.
[0201] Part 3: Deposition-irradiation
[0202] in a third embodiment of the invention, one or more ink(s)
is (are) applied to the substrate in the form of a pattern, and the
ink(s) are transformed into a desired material (eg. metals or
oxides) by action of external heating, light irradiation, or sonic
excitation (see for example FIG. 27).
EXAMPLE 6
[0203] Oxidizing and reducing compounds were mixed together,
applied to the tip and deposited on the substrate at selected
locations by DPN.TM. printing or deposition. the ink mixture was
then heated (either by heating of the whole substrate or by local
probe-induced heating). Specifically, a metal salt and organic
ligand cocktail can be used. a typical ink formulation consisted of
a metal salt (e.g. carboxylate, nitrate, or halide) along with an
appropriate organic Lewis base or ligand (amines, phosphines).
Additives (small molecules such as ethyleneglycol, polymers such as
polyethyleneoxide, PMMA, polyvinylcarbazol, etc) may also be used
that modify the solubility, reactivity, or Theological properties
of the ink. After deposition of the ink mixture, gentle heating in
an ambient or inert environment (40-200.degree. C.) assisted the
dis-proportionation of the salt to form a metallic precipitate and
a volatile organic. This approach enabled deposition of a variety
of metals or metal oxides, for example copper, under mild
conditions with very little organic contaminant [See Sharma et al.,
U.S. Pat. No. 5,980,998, the complete disclosure of which is hereby
incorporated by reference, in particular for the materials
deposited]. Potential pitfalls may occur if the ligand evaporates
from the patterned substrate before reaction takes place. in that
case, the salt-patterned substrate may be exposed to a ligand in a
second step prior to the heating.
[0204] One specific example of the use of this method used DPN.TM.
printing or deposition to pattern palladium acetylacetonate
dissolved in chloroform on oxidized silicon, glass, or
amino-silanized glass. After patterning, a droplet (1 microlitre)
of formamide was placed on the horizontal substrate and heated to
150.degree. C. for 2 min. the resulting metal patterns were stable
towards solvent rinsing (including water, alcohols, and other
non-polar organics) while the salt patterns prior to reduction were
removed by solvent rinsing.
[0205] FIG. 11. (Working Example) FIG. 11 shows AFM images and a
height scan of the patterns before and after treatment with
formamide and heat. Deposition of palladium acetylacetonate
[Pd(acac), 1 .mu.g/mL in CHCl.sub.3 and DMSO] via DPN.TM. printing
on an oxidized silicon substrate, and subsequent reduction by
application of formamide and heat (heating 85.degree.
C.-120.degree. C.) to the patterned surface. Atomic force
micrographs showed (a) a palladium salt pattern before reduction,
(b) the corresponding metal line pattern after heat, and (c) a line
scan indicating the height of the dot patterns.
EXAMPLE 7
[0206] Chromium hexacarbonyl is applied to the tip used for DPN.TM.
printing or deposition and patterned on the photomask. the mask is
then heated above its decomposition temperature (>150.degree.
C.), freeing gaseous carbon monoxide and depositing metallic
chromium. the process may also be used with tungsten and molybdenum
hexacarbonyls. a similar process would use the thermal, spark
plasma or optically assisted decomposition of WF.sub.6 or
WCl.sub.6, which are commercially available chemical vapor
deposition (CVD) agents.
EXAMPLE 8
[0207] an alloy of a liquid metal (i.e. gallium, indium or mercury)
is formed with a soluble metal to deposit, e.g. copper, silver or
gold for Hg. Ternary or quaternary alloys may also be formed e.g.
by adding bismuth, cadmium or zinc. the alloy, which may be liquid
or paste at or near room temperature, is applied to the tip by
appropriate means and deposited in areas to be filled. the alloy is
then decomposed by heating (e.g. mercury is volatilized) or by
chemical oxidation, leaving behind a metal or a simpler alloy with
much higher melting point.
EXAMPLE 9
[0208] a thermoset polymer is deposited by DPN.TM. printing or
deposition and the substrate heated until curing.
EXAMPLE 10
[0209] Related to Example 9, a carbon-rich polymer or its precursor
is deposited via DPN.TM. deposition or printing. the polymer is
then calcinated to afford a graphite-like material. Examples of
useful polymers include polyacrylonitrile (PAN). Non-itumescent
polymers are preferred. the precursor/polymer may be dissolved in a
solvent, deposited on the DPN.TM. deposition or printing probe, and
transferred to the opening to fill. the substrate is then heated
until carbonization of the compound.
[0210] FIG. 9 illustrates deposition of an organic polymeric
solution, followed by calcination into a carbon-rich material;
Pyrolysis of a metalorganic precursor into a metal-rich compound is
also feasible.
EXAMPLE 11a
[0211] FIG. 12 (working example). a photosensitive ink mixture,
such as a photographic emulsion was applied to the opening to be
filled and the substrate was irradiated with light in order to cure
it. Examples included the silver salt emulsion used in the VanDyke
process (ferric ammonium citrate 90 g, tartaric acid 15 g, silver
nitrate 37.5 g, and deionized water 1000 g) or other metal salts
that become light sensitive when placed in the presence of an
organic substance. the emulsion was prepared by (1) mixing ferric
citrate and tartric acid; (2) adding silver nitrate in small
portion while stirring, (3) adding additional water and (4) aging
the solution for 2-3 days. This mixture was then used as an ink in
the DPN.TM. printing or deposition process, dried, and then cured
under a UV lamp to form a metallic material. FIGS. 12a-c
illustrates this method. FIG. 12d is an AFM image of the pattern
generated on amino-silanized glass when the silver nitrate emulsion
was used as an ink. FIG. 12e,f are images of the patterns (lines
and square) that were generated when silver sulfate was substituted
for silver nitrate in the photographic ink mixture. FIG. 12. (a)
Deposition of a silver salt emulsion comprising ferric ammonium
chloride, tartaric acid, silver nitrate or sulfate, and water onto
an amino-silanized glass substrate via DPN.TM. printing, followed
by (b) development by photoreduction under a UV lamp to form (c)
metal nanostructures. See, for example, 300 year old Van Dyke
photographic process. AFM images showed patterns fabricated with
silver nitrate (d) and sulfate (e,f) as the metallic salt.
EXAMPLE 11b
[0212] a photosensitive polymer precursor is applied to the opening
to be filled and the substrate is irradiated with light in order to
cure it. Examples include commercial UV-curable epoxy glues sold
e.g. by Epotex and commercial UV-crosslinked resists
(commercialized for example by Shipley or Clariant).
EXAMPLE 12
[0213] in this embodiment of the invention, a sharp light-guiding
probe is used as the ink deposition means or in conjunction with an
ink deposition means. Once the ink is deposited on the surface, the
chemical or physical state of the ink can then be altered by local
irradiation from a (coherent) light source to afford the desired
product (see FIG. 27 and additional description below regarding
in-situ curing).
[0214] the light-guiding probe may be a pulled optical fiber or
hollow micropipette, which has been optionally coated with an
opaque material (e.g. aluminum), a scanning near-field optical
microscopy probe, or a sharp metallic or metal-coated (apertureless
NSOM) probe placed in the focus of a laser beam, which is capable
of a highly localized amplification of the electromagnetic field
between the probe and surface. the ink can be, for example, a
UV-curable polymer or a UV-curable polymer-based mixture.
EXAMPLE 13
[0215] an ink mixture is applied to a surface in the form of a
nanoscale pattern. Exposure to radiation at appropriate power and
frequency, for instance from a laser, induces formation of a
continuous metal film. an example of such an ink mixture was
described by Stellacci et al (Adv. Mater, 2002, 14, 194), which is
hereby incorporated by reference in its entirety. This metal ink
formulation consists of a metal salt (such as silver
tetrafluoroborate), metal seed particles, photosensitizers, and a
host matrix polymer (such as polyvinylcarbazole) that acts as a
sacrificial reducing agent. After deposition onto a surface this
metal ink formulation can be reduced to solid metal features by
laser pyrolysis. This approach enables deposition of metals such as
silver using relatively low continuous wave laser exposure levels
(1 mW). This approach is also useful for patterning other metals
such as gold and copper with appropriate choice of metal salts and
polymer host. the process is improved by the addition to the ink
mixture of plasticizers such as ethylcarbazole.
EXAMPLE 14
[0216] a suspension of nanometer sized metal nanoparticles is
directly deposited in the form of the nanoscale structure or film
on a substrate and then irradiated to generate continuous metallic
structures. One example would use thiol-protected gold
nanoparticles such as those described by Ali et al (Langmuir 2002,
18, 872-876), or palladium particles such as those described by
Hidber et al (Langmuir 1996, 12, 1375-1380), both of which are
hereby incorporated by reference.
EXAMPLE 15
[0217] a low-melting-temperature thermoplastic polymer is applied
to a heated probe and deposited while hot and fluid. Cooling of the
polymer on the cold substrate affords the final feature. the
polymer may be loaded with a thermostable filler.
[0218] Part 4: Colloid Deprotection and Fusion
EXAMPLE 16
[0219] in another embodiment of the invention, a solution of
encapsulated nanoparticles is deposited in the area to pattern.
Encapsulation may be provided by a (a) a small organic ligand bound
to the particle (e.g. pyridine on copper nanoparticles); (b) a
monolayer self-assembled on the nanoparticles (e.g. alkanethiols on
gold nanoparticles; see Wuelfing et al., Chemistry of Materials,
13(1): 87-95, 2001); (c) a polymer adsorbed by Van de Waals or
electrostatic forces (e.g. PEG). the nanoparticles are deprotected
and fused together by heating to form opaque metallic
structures.
[0220] Because the sintering temperature is much lower than the
bulk melting temperature, due to the Kelvin effect observed with
small diameter clusters ["Sintering of alkanethiol-capped gold and
platinum nanoclusters", J. E. Martin et al. J Phys. Chem. B
107(2):430-434, 2003], such technology is practical even for
temperature-sensitive photomasks.
[0221] Micrometer-scale equivalents of this patterning technique
can be carried out: See for example "Microstructuring by printing
and laser curing of nanoparticle solutions", Bieri et al., Applied
Physics Letters 82(20);3529-3531, 2003 and "laser writing in
polarized silver nanorod films" O. Wilson et al., Advanced
Materials 14(13-14):1000, July 2002.
[0222] an alternative to direct deposition of ligand-stabilized
metallic nanoparticulate inks is the deposition of nanoparticle
beds in a layer-by-layer fashion, with the aid of
oppositely-charged metal ions or polyelectrolytes. See FIG. 7,
which shows nanometer-scale deposition of metal structures by
deposition of ligand-stabilized metallic or metal oxide
nanoparticles, followed by thermolysis-induced ligand deprotection
and particle fusion. the nanoparticles are optionally deposited in
a controlled, layer-by-layer fashion by successive layering with an
adhesive layer (oppositely-charged metal ions or
polyelectrolytes).
[0223] FIG. 8 illustrates deposition of a mixture of a (polymeric)
precursor and metal colloids, followed by UV curing. This method
may use commercial preparations (silver paints). Air-curable or
thermoset polymers, sol-gels, and oxide nanoparticles may also be
used.
[0224] in addition, copper nanoparticles protected by
nitrogen-containing aromatic compounds can be deposited and then
heated to >300.degree. C. [Winter 2001].
[0225] Part 5: Direct Electrodeposition
[0226] in another embodiment, a bias is applied between the
deposition nanolithography probe coated with a redox compound and
the substrate, which must be conductive or rendered so e.g. by
previous application of a conductive film (such as indium tin
oxide, ITO).
EXAMPLE 17
[0227] a metal is deposited from the corresponding salt under
electrochemical bias. Li et al. described a method of depositing
metal nanostructures via DPN wherein a metal salt such as
HAuCl.sub.4 is delivered to and reduced simultaneously at the
substrate surface via a nanoscale electrochemical reaction [Li,
2001]. See FIG. 4. FIG. 4 illustrates metal deposition via DPN.TM.
printing under bias control. a voltage bias is applied between a
conductive probe, for example a metal-coated atomic force
microscopy (AFM) tip, and the substrate, which must be rendered
conductive. the probe has been coated beforehand with a
redox-active ink, for example a metal-ligand complex. Without
wishing to be bound by theory, it is believed that the meniscus
that can naturally form between the probe and substrate may in some
cases serve as a nanometer-scale, mobile electrochemical cell, in
the manner of scanning electrochemical microscope probes [Bard
1999]. the bias-applying power supply may be a voltage source, a
current source, and may be regulated as a function of the probe
speed and the gap resistance.
[0228] a similar method may be used to fill defect voids in chrome
structures with metals such as copper, gold, and platinum. Multiple
passes over the defect region will be performed to build up the
metal to desired height in a highly controlled manner. This method
can be appropriate for repair of voids in chromium features due to
the conductive nature of material surrounding the defect site. in
this case, it may be possible to use a second, proximal probe tip
to supply bias.
[0229] Part 6: Deposition of Optically Transparent and Opaque
Materials
[0230] in this part of the invention, the additive repair of
optically transparent substrates, such as quartz or sapphire, is
disclosed. the objective is to improve the transmissibility of and
to correct for phase shift errors of a transparent substrate that
(a) presents a void; or (b) presented a bump but has been
overrepaired.
[0231] as in opaque material repair methods, the void is either
filled directly with the material or filled with a precursor which
is then processed to afford the desired material.
[0232] Materials to be considered as fillers should have an optical
transmissibility and an index of refraction at the lithography
wavelength and a thermal expansion coefficient close to these of
the substrate. Preferably, the material being deposited has the
same or generally the same chemical composition as its
substrate.
EXAMPLE 18
Spin-on-Glass
[0233] Spin-on glasses (SOG) are liquid formulations forming a
glassy substance after baking. Common formulations include, for
example, silicates, phosphosilicates or siloxanes doped with
arsenic, antimony, boron or phosphorous compounds, as precursor to
silica- or silicate-rich materials. Commercial precursor solutions
are provided e.g. by Honeywell Electronic materials.
EXAMPLE 19
Sol-gels
[0234] in another example, a sol-gel precursor is patterned and
converted into an opaque oxide or metal. Su et al described
deposition of solid state structures using sol-gel metal alkoxide
precursor inks via DPN.TM. printing or deposition [Su et al., J.
Am. Chem. Soc., 124(8), 1560-1561, February 2002].
[0235] the soft metal-organic hybrid structures were decomposed in
a final step in the presence of oxygen to yield the corresponding
metal oxide, see FIG. 5, which illustrates deposition of metal
oxides by DPN.TM. printing-depositing sol-gel inks, such as alkoxy
complexes and polymers thereof (see provisional patent application
in reference 13 above and its counterpart US patent publication
2003/0162004 cited below). the metal-organic hybrid structures
formed during patterning are either used as is, or thermolyzed to
yield the corresponding oxide. Metal/reduced form patterns may be
obtained by pyrolysis in a reducing environment.
[0236] a similar methodology may be used to deposit opaque metal
structures by heating instead in a reducing environment. Layers
5-10 nm in height will be written and thermolyzed to yield opaque
structures. Potential pitfalls in this method are the use of high
temperatures. This pitfall may be avoided by using no or a partial
bake and make a direct use of the metalorganic polymer being
deposited.
[0237] the following references may be used:
[0238] "Sol-gel science: the physics and chemistry of sol-gel
processing", C. J. Brinker, G. W. Scherer, published by Harcourt in
1990.
[0239] "Moving beyond molecules: Patterning solid-state features
via dip-pen nanolithography with sol-based inks", M. Su, X. G. Liu,
S. Y. Li, V. Dravid, C. Mirkin, JACS 124(8): 1560-1561, 2002.
[0240] U.S. Patent Application No. 2003/0162004 a1 published to
Mirkin, Chad a. et al. ("Patterning of solid state features by
direct write nanolithographic printing")
EXAMPLE 20
Opaque Structures Prepared by Sol-Gel Methods
[0241] the sol-gel precursor may be mixed with a nanoparticulate,
for example carbon black, or other opacifying agents to opacify the
resulting deposit.
[0242] the following references may be used and are incorporated
herein by reference:
[0243] "Preparation of a silica gel carbon black composite by the
sol gel process in the presence of polymer-grafted carbon black",
K. Fujiki et al., J. Materials Science, 33(7): 1871-1879, 1998.
[0244] "Carbon black/alumina gel composite: Preparation by sol-gel
process in the presence of polymer-grafted carbon black and its
electric properties", N. Tsubokawa et al., Journal of Polymer
Science Part a-Polymer Chemistry 37(18):3591-3597,1999.
[0245] Additional description and working examples are provided to
which can be used to repair masks, repair photomasks, fabricate
masks, fabricate photomasks, and prepare nanostructures. for
example, binary masks were prepared on silicon oxide.
[0246] FIG. 13
[0247] FIG. 13 illustrates a further schematic for a sequence of
events in mask repair by nanodeposition; (1) the mask is inspected,
e.g., using optical microscopy; If found to be defective, (2) the
pellicle protecting the mask is removed; (3) the mask is cleaned of
pellicle residue and other organic and/or inorganic contaminants;
(4) the mask is placed in the repair apparatus, and aligned so that
the previously identified defects could be precisely located; (5)
the nanolithography probe is directed to the first defect; a first
deposit is made; (6) If necessary, the wafer is submitted to an
external process step, such as heating, UV irradiation, exposure to
a chemical vapor, and the like that will induce layer curing. the
process is repeated for each layer and each defect as required. (7)
the mask is optionally cleaned, inspected (as in step 1) for
unrepaired defects and reintroduced in fabrication if judged of
sufficiently good quality such as, for example,
production-quality.
[0248] FIGS. 14A and 14B
[0249] FIGS. 14A and 14B illustrate formation of a layered stack,
wherein the resulting height and absorption are consistent with the
photomask. Schematic illustrating [a] a method of stacking multiple
layers to form a pattern of sufficient height, when one may not be
made in a single deposition step; and [B] a method of enhancing the
pattern as deposited to meet edge placement, line edge roughness,
sidewall angle and/or thickness objectives (and thus optical
properties) for the repair. [a] (a) a first layer of a first ink is
deposited via direct-write deposition nanolithography in a clear
defect. the leftmost object represents a preexisting mask pattern.
(b) the ink is cured, e.g. by chemical reaction, heating or
exposure to UV light, so that (c) another layer of the same or a
different ink may be deposited above the first. (d) the process may
be repeated once or multiple times, until an appropriate height is
reached. [B] (e) the geometric characteristics of a pattern formed
by deposition nanolithography (which may be composed of one or
multiple layers) is improved by locally applying a high contact
force, depositing a chemical etchant or by a combination of both
(in a manner similar to chemical mechanical polishing). Step (f)
demonstrates the possible result of lapping along an edge to
achieve a high sidewall angle, while (g) illustrates equalizing the
pattern height and decreasing its roughness.
[0250] Nanolithography can be used to deposit a capping layer on
top of an existing deposit, the function of the capping layer
being, for example, to protect the deposit during subsequent mask
cleaning steps and promote adhesion of said deposit to the
substrate. for example, the capping layer may be, for example,
sol-gel precursor deposited on a metallic deposit.
[0251] Part 7: Repair of Advanced (PSM) Photomasks and
Next-Generation Lithography Masks
[0252] Additional description about masks is provided. Many of the
techniques for repair of COG also apply to advanced photomask
(APSM, AAMPSM) and NGL mask technologies (EUV, EPL, and the like),
while there are great economic incentive to repair these kinds of
masks.
[0253] Phase shifting masks take advantage of destructive
interference at pattern edges to improve contrast. Alternating
Aperture PSMs, also called strong-shifters, are fabricated by
etching 180'-phase-shifting windows in alternating clear areas of
the quartz mask. Repair technologies in this area focus on
repairing substrate defects, such as removing quartz bumps and
filling quartz pits with a quartz-like material ["Alternating phase
shift mask defect printability for 130 nm and 100 nm KrF
lithography", Kim et al., International SEMATECH, May 19, 2000].
This may be achieved with sol-gel deposition methods.
[0254] Attenuating PSM (weak-shifters) relies on the deposition of
a partially transmitting, phase-shifting material (e.g. molybdenum
silicide). Light diffracted from a clear opening in the photomask
will destructively interfere with light leaking from the
phase-shifted areas, improving contrast. Additive repair of the
phase-shifting layer relies on the deposition of a layer with
similar overall optical properties (transparency, index of
refraction), which may be achieved by precise control of the
chemistry and the thickness of the patch. the deposition of
nanoparticle embedded in a transparent sol-gel-like inorganic
binder has been described in "Electrical characterization of
polymethylsiloxane/MoSi.sub.2-derived composite ceramic", J.
Cordelair, P. Greil, J. Am. Cer. Soc. 84(10):2256-2259, 2001.
[0255] Next Generation Lithographies (NGL) are being developed to
replace DUV/VUV lithography at the 2006-2013 time horizon for
critical dimensions (CD) inferior to 70 nm. the primary contender
is Extreme UV (EUV, 14.6 nm). Other technologies, including
electron projection lithography (EPL), including SCAPEL, and X-ray
lithography (1 nm) are being considered. in addition, Nanoimprint
Lithography (NIL), a stamping technology, might also find a niche
market for small-series applications. in this method, a mask is
used as a mold (also called a mold) to press or stamp in a
structure. See, for example, U.S. Pat. Nos. 5,772,905 and 6,309,580
to Chou. Repair and fabrication of nanoimprinting masks are part of
the present invention.
[0256] EUV masks currently being developed consist of diffractive
reflectors containing as many as 40 alternating layers (e.g.
Mo/Si), coated with a buffer layer (typically silicon oxide,
silicon oxynitride (100 nm), sometimes C (75 nm) films) and an
absorber pattern (typically Cr or TaN, 30-50 nm thick) [Hector et
al., J. Vac. Sci. Tech. B, 19(6):2612-2616, and J. R. Wasson et
al., J. Vac. Sci. Tech. B, 19(6):2635- Nov-December 2001].
[0257] Because of the nature of the absorber and the presence of a
protecting buffer layer on the EUV mirror, the nanodeposition
repair techniques proposed for traditional photomasks (metal
deposition, for example) can be transferable to EUV masks.
Furthermore, it is noted that most materials strongly absorb at EUV
wavelengths, facilitating the choice of the chemical composition of
the repair patch.
[0258] X-ray lithography and EPL masks are typically thin membranes
(e.g. Si) supporting an absorber pattern (e.g. Au) or stencils. in
the former case, metal deposition methods, as disclosed above can
be used.
[0259] in NanoImprinting Lithography (NIL), a nanometer-scale mold
is pressed against a soft substrate in the manner of a waffle-iron
["Imprint of sub-25 nm vias and trenches in polymers", S. Y. Chou,
P. R. Krauss, P. J. Renstorm, Appl. Phys. Letters
67(21):31114-3116, 1995; "Multilevel nanoimprint lithography with
submicron alignment over 4 in. Si wafers", W. Zhang and S. Y. Chou,
Appl. Phys. Letter 79(6):845]. NIL equipments are available from
Nanonex, EV Group, Obducat, and Molecular Imprints, Inc. the later
company commercializes Step & Flash.TM. Imprint Lithography
(S-FIL.TM.), wherein a transparent stamp is pressed in contact with
a substrate coated with a curable photopolymer and illuminated with
UV light. the stamp, which has been previously coated with a
release layer, is then removed, yielding a photopolymer imprint.
Further etching steps transfer the pattern to the underlying
substrate and the process is repeated with another wafer.
Stamps/molds are typically made of quartz (S-FIL), silicon dioxide
on silicon, with etched features 100-250 nm deep, and are typically
prepared by e-beam lithography (PSM mask technology) followed by
reactive ion etching (RIE). Those skilled in the art will recognize
that similar masks are used by several variants of that methodology
(including microcontact printing). for this invention, these molds
and stamps are masks and can be fabricated and repaired by the
methods described herein.
[0260] Because NIL masks/molds are most frequently made of the same
materials than photomask blank, the photomask substrate repair
methods outlined above (esp. sol-gel) are directly applicable.
[0261] the programmed shrinking of mask feature sizes and stringent
critical dimension control requirements make defect inspection and
repair absolutely critical for advanced mask technologies. a
high-precision tool, capable of nanometer-scale XY control and able
to process multiple layers with high Z resolution is therefore
required for the fabrication and repair of masks for emerging
lithographies.
[0262] in contrast with photomasks or EUV masks, which have a 4:1
or 5:1 mask-to-wafer-feature-size ratio, NIL masks are 1:1.
Already, mask feature sizes are beyond the capabilities of
traditional repair tools. Direct-write nanolithography is therefore
extremely attractive for the repair of NIL molds.
[0263] Part 8: Methods to Enhance the Rate of Ink Deposition From a
Tip and Its Ink Capacity
EXAMPLE 21
Enhanced Deposition Using a Polymer-Coated "Dpn Stamp Tip"
[0264] Photomask repair via deposition nanolithography requires the
deposition of a sizable amount of materials (about a thousandth of
a micron cube), compared to amounts generally present on an
AFM-cantilever-style silicon nitride tip in a minimum amount of
time. it is therefore advantageous to modify DPN probes in a way
such as (1) more ink may be retained on the tip, when delivered to
it; and (2) more ink may be deposited, when the tip is used.
[0265] One modification involves coating the tip with a semi-porous
and/or gelatinous layer, for example a siloxane polymer or
copolymer like polydimethylsiloxane (PDMS) or a copolymer thereof.
Without wishing to be bound by theory, it is believed that (1) the
polymer forms a spongious coating that stores ink; and (2) that the
contact area between the tip and sample is increased by the
polymeric coating, which in turn increases the overall rate of ink
deposition.
[0266] in the following working examples, the following recipe for
preparing sol-gel ink was used: 40 .mu.L of MEOS (Methoxy Ethoxy
Ortho Silicate) and 10 .mu.L of 10% Pluronic (a block copolymer of
ethylene oxide and propylene oxide, commercialized by BASF,
Ludwigshafen, Germany) made in water. After depositing sol-gel
structures, they were cured for 6 min at 120.degree. C. after
deposition. After the curing, the nanostructures were resistant to
mild sonication, piranha (3:1 mixture of concentrated sulfuric acid
and hydrogen peroxide) and RCA2 treatment (5:1:1 mixture of water,
hydrogen peroxide, and ammonium hydroxide).
[0267] for depositing metal ink in the features, the following
procedure was used: a saturated solution of sodium
tetrachloropalladate II was prepared in Ethylene Glycol (80% in
water). After deposition, the metal salt was reduced to metal by
exposing it to DMAB vapor for 15-30 sec and then heating the
substrate to a temperature of 120.degree. C.-160.degree. C. for 10
min. the method of reducing a metal salt in presence of an alcohol
is based on the poylol process.
[0268] the following procedure illustrates the fabrication of a
PDMS-coated tip (see FIG. 24):
[0269] a Si or Si/SiO.sub.x substrate (2.times.2 cm.sup.2) and a
Si.sub.3N.sub.4 tip were immersed into a boiling mixture of
H.sub.2O.sub.2:NH.sub.4OH:H.sub.20,1:1:5 (v:v:v) for about one
hour, then rinsed with double deionized H.sub.2O (provided by e.g.
Milli-Q equipment) and dried in a flow of pure nitrogen
(N.sub.2).
[0270] a silicone elastomer and a silicone elastomer curing agent
(Sylgard 184 silicone elastomer kit, Dow Corning corporation,
Midland, Mich.) was mixed together in a 10:1 ratio (w/w). the
resulting elastomer is essentially pure polydimethylsiloxane.
[0271] a droplet of the mixture was placed onto the cleaned Si or
Si/SiOx substrate and put onto the sample stage of an atomic force
microscope. a clean Si.sub.3N.sub.4 microcantilever (available from
Nanolnk, Inc.) was mounted into the tip holder. the Si.sub.3N.sub.4
tip was placed in contact with the silicone mixture, then
retracted. the procedure was repeated again.
[0272] the coated tip was placed in an oven for 12 hours at
60-70.degree. C. to completely cure the polymer coating.
[0273] an optical image of a cantilever terminated by such a tip is
shown in FIG. 25.
[0274] Before lithography, the finished tip is inked by dipping in
an appropriate solution and drying it in air.
[0275] Standard Si.sub.3N.sub.4 tip may be exchanged with a
polymer-coated tip without need for a retuning of experimental
parameters.
[0276] Advantages of coated tips include:
[0277] the coating procedure is relatively and generally easy,
low-cost and has a high success rate (near 100%).
[0278] Nanodeposition with coated tips combines the advantage of
DPN and micro-contact printing (.mu.CP), but has higher resolution
(sub-100 nm) than .mu.CP.
[0279] Such a coated tip may pattern fully liquid inks or ink still
dissolved in a solvent.
[0280] Coated tips can still be used for AFM imaging.
[0281] as opposed to methods described in "Scanning probe with
elastomeric (PDMS) tip for scanning probe microcontact printing
(SP-uCP), X. Wang, K. Ryu, D. Bullen, J. Zou, C. Mirkin, C. Liu,
(Langmuir, 2003) no lengthy tip fabrication procedure is
required.
[0282] Other polymers and non-polymeric compounds may be used as
the tip coating as well, including (a) alkyl- and aryl-siloxane
type polymers and (b) fluorinated polymers. in general, polymers
which were found suitable for microcontact printing [Wilbur et al.,
Advanced materials 6(7-8):600-604, 1994] and similar soft
lithography can be used.
[0283] Working Examples With PDMS Tip (Polydimethylsiloxane):
[0284] the procedure is illustrated in FIG. 24. a piece of Si or
Si/SiOx substrate (2.times.2 cm.sup.2) and a Si.sub.3N.sub.4 tip
were immersed into a boiling mixture
(H.sub.2O.sub.2:NH.sub.4OH:H.sub.2O=1:1:5 (v:v:v)) for about one
hour, then rinsed with Milli-Q H.sub.2O and dried with pure
N.sub.2.
[0285] Mixture 1: completely mixed silicone elastomer and silicone
elastomer curing agent (Sylgard 184 silicone elastomer kit, Dow
corning corporation, Midland, Mich., 48686-0994) at a ratio 10:1
(w/w). Took a droplet of the mixture 1 onto the cleaned Si or
Si/SiOx substrate and put it onto the sample stage of an AFM.
Mounted a clean Si.sub.3N.sub.4 into the tip holder. Moved the
Si.sub.3N.sub.4 tip to touch the mixture 1 and retracted the tip,
repeated it again. Took the tip out and put it in an oven for 12
hours at 60-70.degree. C. Took the tip out and the DPN stamp tip
was fabricated (see the optical image, FIG. 25).
[0286] the experimental conditions in the photomask experiment done
with a DPN stamp tip was the same as that done with a
Si.sub.3N.sub.4 tip. Only changed the Si.sub.3N.sub.4 tip to DPN
stamp tip.
[0287] Besides PDMS, other hydrophobic polymers, elastic polymers,
and thermosetting systems can be used as well, including
polysiloxane type polymers and alkyl- and aryl-siloxane type
polymers and flourinated polymers. in general, polymers which are
suitable for microcontact printing and soft lithography can be
used.
[0288] the following figures provide additional working examples of
the invention:
[0289] FIG. 15
[0290] FIG. 15 (working example) shows a zoomed out view of the
deposited structures. Sol gel structures were written in one of the
smallest features in binary mask (test masks can be obtained from
commercial suppliers). the features (5 holes) in the mask were one
micron by two microns. Nanostructures were created in smaller
features also.
[0291] FIG. 16
[0292] FIG. 16 (working example) shows the target feature used for
deposition of sol-gel structures on a test mask. the dimensions of
the hole were length (two microns), width (one micron), and height
(75 nm).
[0293] FIG. 17
[0294] in FIG. 17 (working example), dots were created
demonstrating the control over height of the feature and the
registration. the dimensions starting from the top feature:
1 Height (nm) Width (nm) Time (minutes) 17 128 3 17.5 150 3.5 18.5
163 4
[0295] FIG. 18
[0296] in FIG. 18 (working example), a high dot 45.3 nm tall was
created in the test mask by holding the tip coated with sol-gel for
15 minutes. This demonstrated the ability to create very high
nanostructures without losing control over the length and width
dimensions (x and Y).
[0297] the height is not particularly limited by this working
example. the height can be, for example, about 5 nm to about 200
nm, and more particularly, about 10 nm to about 200 nm, and more
particularly, about 10 nm to about 100 nm, and more particularly,
about 25 nm to about 75 nm. it can be at least 30, at least 45, at
least 55, at least 100, or at least 150 nm high. the number of
layers is not particularly limited but can be, for example, two to
twenty layers, or more particularly, three to fifteen layers. it
can also be a single layer, forming an integral structure.
[0298] FIG. 19
[0299] in FIG. 19 (working example), three lines were created,
including one line substantially exactly alongside the defect edge.
the dimensions for the lines starting from the left were:
2 Height (nm) Width (nm) Time (minutes) 15 162 6 10 150 5 5 138
4
[0300] FIG. 20
[0301] FIG. 20 (working example) illustrates the target hole on
FIBics Structures for deposition of metal salt and sol-gel
structures. the hole was about 200 nm wide and about 100 nm
deep.
[0302] FIG. 21
[0303] FIG. 21 (working example) illustrates the filling up of a
hole in features made with FIB. the average height of the feature
deposited was 46 nm. a silicon nitride tip was used in this
experiment. the dwelling time as 14 minutes. the deposited
structure was cured at 120.degree. C. for 6 minutes.
[0304] FIG. 22
[0305] FIG. 22 (working example) illustrates the metal salt filled
in FIBics Structures. at the top, another empty hole is shown. at
the bottom, a hole is shown which is filled with metal ink. the
deposition was carried out with use of a PDMS tip. the image was
taken after all the reduction steps (DMAB, heating) and after mild
sonication. the height of the filled nanostructure is over 100
nm.
[0306] FIG. 23
[0307] FIG. 23 (working example) illustrates building up of metal
structure by layering, layer by layer. First, a saturated solution
of palladium chloride prepared in 80% ethylene/20% water was
deposited using a PDMS-coated tip. the sample was taken out of the
instrument, exposed to DMAB vapor for 15-30 seconds, and heated to
120.degree.-160.degree. C. the sample was replaced in the
instrument and the procedure was repeated again. Each layer was
about 2.2 nm in height; the stack formed by the two layers was
about 4.6 nm high.
[0308] FIG. 24
[0309] FIG. 24 provides a schematic representation for fabrication
of PDMS-Coated DPN Stamp tip.
[0310] FIG. 25
[0311] FIG. 25 (working example) provides optical microscopy images
of a PDMS-Coated DPN stamp tip.
[0312] for working examples, all chemicals were bought from Aldrich
(St. Louis, Mo.), unless otherwise noted.
[0313] Additional description of the invention is provided
below.
[0314] Recent examples of photomask repair in the patent
application publication literature includes the following
references which can be used by one skilled in the art to practice
the invention:
[0315] (a) 2003/0127441 to Haight et al. (published Jul. 10,
2003)
[0316] (b) 2003/0087200 to Border et al. (published May 8,
2003)
[0317] (c) 2002/0122992 to Kanamitsu et al. (published Sep. 5,
2002)
[0318] (d) 2002/0009843 to Kyushuo et al. (published Jan. 24,
2002)
[0319] Issued U.S. Patents include 6,165,649 to Grenon et al (Dec.
26, 2000) and U.S. Pat. No. 6,139,993 to Lee (Oct. 31, 2000).
[0320] a mask as used herein includes a photomask which is sized to
expose an entire semiconductor wafer or substrate containing an
entire integrated circuit, as well as a mask, such as a reticle,
which is sized to expose only one area on the wafer or substrate,
such as a single chip or die. the reticle is used to expose plural
chips or die on a wafer or substrate by a step and repeat exposure
method. Furthermore, the photomask is not limited to masks used for
optical exposing radiation, but also includes masks suitable for
UV, EUV, X-ray and electron beam exposure.
[0321] the present invention provides nanometer-scale functional
features (including deposits, filled openings, and etched
openings), as well as the enabling methods and apparatus. Examples
of specific features to be fabricated include:
[0322] (a) Defect repair patches in transmission photomasks and
reflection photomasks such as these used for extreme UV
lithography. This includes the deposition of opaque or transparent
materials, or their etching. for example, this includes building up
or reducing the thickness of the partially transmitting material,
such as MoSi.sub.2 in an attenuating PSM or building up or reducing
the thickness of the transparent material regions or windows in the
strong PSM to adjust the phase shift of the radiation to as close
as possible to 180 degrees. the photomasks may also be manufactured
by this method, such as by depositing opaque or partially
transmitting patterns on a transparent mask substrate or by
building up or removing material in phase shift windows in strong
PSMs to obtain a 180 phase difference due to the thickness
difference of the PSM regions.
[0323] (b) Vias, lines and defect thereof, in microelectronic
circuits, the application being the repair or fabrication of
patterns of high-value chips; for example, this includes depositing
metal into undesired openings in metal or metal silicide
interconnect metallization in semiconductor or other solid state
devices to repair the metallization, as well as to remove undesired
deposits, such as undesired short circuits between metallization
lines. Alternatively, a very thin gate insulating layer, such as a
less than 10 nm thick gate insulating layer may be selectively
deposited using an ink which forms an insulating layer, such as
silicon oxide, silicon nitride or oxynitride and/or aluminum oxide.
Alternatively, ultra narrow gate electrodes, such as MESFET or
MOSFET gate electrodes, having a width of less than 10 nm may be
selectively deposited using an ink which forms a conductive gate
material, such as a metal or silicide.
[0324] (c) Filled defects in microelectromechanical systems (MEMS),
the application being the repair, modification or testing of
prototypes. for example, cantilevers and membranes in MEMS may be
repaired or manufactured in this manner.
[0325] Optical properties are important for photomask repair. for
repair of clear defects, the repair is opaque or absorbent at the
wavelengths using during lithography. for repair of opaque defects,
good transmissibility at the lithographic wavelength is used. it is
desired that the repaired areas introduce minimal phase error.
Preferably, the repaired area does not show up as a defect during
inspection (e.g., there is a lack of scattering when observed; the
repair should be opaque at the inspection wavelength.)
[0326] in addition, the deposit should not be damaged by mask
cleaning steps during the lifetime of the mask. the deposit should
adhere to the substrate and not be removed by a washing step, and
it should withstand trace organics removal by Piranha or
concentrated sodium hydroxide solutions. in general, the repair
should not be damaged during lithography (e.g., by high-fluence UV
irradiation) or at least should last for a significant fraction of
the expected lifetime of the mask.
[0327] With respect to metrology, the pattern should be positioned
in defect sites with high accuracy and repeatability; the lateral
dimensions and height of the pattern should be controlled with high
resolution; positioning and dimension control should be preserved
when depositing pattern in successive steps/layers; the sidewall
angle of the pattern should be close to 90.degree. C. and the line
edge roughness should be small. that which is acceptable can vary
with the lithography and the technology node.
[0328] Photomask repair can be carried out with use of depositing
of sol-gel inks and metal inks using a polyol process. in addition
to chromium on glass (COG) masks, advanced COG-derived technologies
(PSM, OPC) and of other techniques (EUV, x-ray masks) can be used.
MoSi2, PSM, AAPSM, EUV, and EPL are all within the scope of the
invention. There can be greater economic incentive to repair these
kinds of masks.
[0329] for advanced photomask repair, the following reference can
be used: "Issues for advanced reticle fabrication: (You want that
reticle when?)", J. G. Maltabes, Future Fab, Vol. 11, June
29.sup.th 2001]."
[0330] for NanoImprinting Lithography masks repair: in
NanoImprinting Lithography (NIL), a nanometer-scale mold is pressed
against a soft substrate in the manner of a waffle-iron ["Imprint
of sub-25 nm vias and trenches in polymers", S. Y. Chou, P. R.
Krauss, P. J. Renstorm, Appl. Phys. Letters 67(21):31114-3116,1995;
"Multilevel nanoimprint lithography with submicron alignment over 4
in. Si wafers", W. Zhang and S. Y. Chou, Appl. Phys. Letter
79(6):845]. NIL equipments are available from Nanonex, EV Group,
Obducat, and Molecular Imprints, Inc. the later company
commercializes Step & Flash.TM. Imprint Lithography
(S-FIL.TM.), wherein a transparent stamp is pressed in contact with
a substrate coated with a curable photopolymer and illuminated with
UV light. the stamp, which has been previously coated with a
release layer, is then removed, yielding a photopolymer imprint.
Further etching steps transfer the pattern to the underlying
substrate and the process is repeated with another wafer.
Stamps/molds are made of quartz (S-FIL), silicon dioxide on
silicon, with etched features 100-250 nm deep, and are typically
prepared by e-beam lithography (PSM mask technology) followed by
reactive ion etching (RIE). Because NIL is a 1:1 replication
technology, mask feature sizes are beyond the capabilities of
traditional repair tools. Direct-write lithography is therefore
extremely attractive for the repair of NIL molds. Those skilled in
the art will recognize that several variants of that methodology
exist that make use of similar masks. This includes microcontact
printing molds.
[0331] for embodiments with carbon black in sol-gel, the following
references can be used: "Preparation of a silica gel carbon black
composite by the sol gel process in the presence of polymer-grafted
carbon black", K. Fujiki et al., J. Materials Science, 33(7):
1871-1879,1998. "Carbon black/alumina gel composite: Preparation by
sol-gel process in the presence of polymer-grafted carbon black and
its electric properties", N. Tsubokawa et al., Journal of Polymer
Science Part a-Polymer Chemistry 37(18):3591-3597, 1999.
[0332] for embodiments in a MoSi.sub.2 attenuating phase-shifting
photomask repair: "the deposition of MoSi.sub.2 nanoparticle
embedded in a transparent inorganic binder has been described in
"Electrical characterization of
polymethylsiloxane/MoSi.sub.2-derived composite ceramic", J.
Cordelair, P. Greil, J. Am. Cer. Soc. 84(10):2256-2259, 2001."
[0333] for embodiments with a near-field photomask repair:
[0334] "Near-field photomask repair with a femtosecond laser",
Lieberman et al., Journal of Microscopy, Vol. 194, Pt 2/3, May/June
1999, pp. 537-541]
[0335] for embodiments with Chemical-Mechanical Etching of opaque
defects, the following references can be used: Examples known in
the art include the deposition of a chemical etchant from a hollow
pipette. See for example "Fountain pen nanochemistry: Atomic Force
control of chrome etching", a. Lewis et al. Applied Physics Letter
75(17), 2689, Oct. 1999 and references herein, hereby incorporated
by reference. Methods of making said nanopipette can be found in
U.S. Pat. No. 6,600,856 to Lewis, and U.S. Pat. No. 6,396,966 to
Lewis et al.
[0336] Localized Deposition of Metal With Micropipette
[0337] See also "Localized electrochemical deposition of metals
using micropipettes", a. D. Mueller et al. Thin Solid Films 336
(2000), 32-36.
[0338] U.S. patent application 2002/0122873 ("Nanolithography
methods and products therefor and produced thereby", Mirkin et al.)
describes methods to make and use of aperture probe tip capable to
delivering
[0339] for methods to repair defects in substrate: Quartz Bump
Chemical Etching: in this working example, BOE (buffered oxide
etch, a mixture of ammonium fluoride and hydroxide well-known to
the art) is applied to a silicon nitride tip. Said tip is brought
in contact with the area of the photomask substrate to be repaired.
BOE etches silicon dioxide much quicker than silicon nitride, with
a selectively better than 200:1. the process is repeated until the
quartz bump is totally removed. Optionally, a compound capable of
neutralizing excess etchant may be applied with a second tip. the
reticle is optionally washed to eliminate residues.
[0340] Quantitative Requirements for Defect Repairs
[0341] the following reference can be referred to: -"Near-field
optical photomask repair with a femtosecond laser", Lieberman et
al. Journal of Microscopy Vol. 194, Pt. 2/3, May/June 1999, pp.
537-541.
[0342] High-resolution repair methods can be used. in preferred
embodiments, the following parameters can be used: an edge
placement better than 50 nm, an accuracy of 2 um over the wafer, a
scanner repeatability (pattern placement) of 20 nm, a 400 nm
aperture (resolution), and an edge placement equal to 10% of the
CD.
[0343] Handle data from mask inspection tools
[0344] Handle 6".times.6" mask plates; >5".times.5" writing
area
[0345] the mask wafer should not be submitted to temperature above
200.degree. C.
[0346] in-Situ Curing Methods
[0347] in many aforementioned embodiments, post-deposition steps,
in which one or more inks are transformed from their as-deposited
chemical and/or physical state into another (by irradiation, by
heating, reaction with a liquid, gas or vapor, etc . . . ), are
carried out to give the deposit its permanent properties. for
example, the deposit may be reduced, polymerized, or sintered to
obtain the appropriate opacity, chemical resistance and substrate
adhesion.
[0348] the present embodiment of the invention relates to "in-situ"
curing methods, wherein this transformation is triggered locally
and/or within the nanolithography process flow. it further relates
to methods to cure the ink deposited on the substrate, but not the
ink still present on the tip. for example, this methodology would
eliminate the need to remove the substrate (e.g. mask) from the
nanolithography apparatus to submit it to an external processing
step.
[0349] the methods disclosed herein are especially useful, when
more than one layer must be deposited to meet the desired
specifications (thickness, transparency). Building structures
layer-by-layer is disclosed above.
[0350] in a first embodiment of this invention, a first probe is
used to deposit a first ink in the area of interest (e.g. defect).
a second probe is then brought in the vicinity of the first deposit
and delivers a second ink. the process may be extended to three or
more probes.
[0351] in a preferred embodiment, the inks are chosen to be
chemically reactive with or in the presence of one another (in the
later case, one or more chemical compounds in one ink catalyze the
chemical reaction of one or more chemical compounds of another
ink). for example, inks 1 and 2 could comprise a metal salt and a
reducing agent, respectively. Mixing inks 1 and 2 results in the
formation of a metal pattern while minimizing the need for heating
or exposure of the whole mask to a reducing agent vapor. See FIG.
26.
[0352] in another embodiment, the inks are deposited in such a way
that a gradient in chemical composition and therefore physical
properties is present in the resulting pattern. Preferably, a
vertical gradient is established.
[0353] Preferably, the probes used to deposit multiple inks belong
to the same probe array and have been inked by dipping into an
array of ink wells containing said inks, as disclosed in U.S.
Patent Provisional Application No. Serial No. 60/425,252 filed Nov.
12, 2003 to Cruchon-Dupeyrat et al.
[0354] the process may be repeated one or more times and may be
combined with layer-by-layer deposition.
[0355] in a fourth embodiment of this invention, a transformable
(e.g. photosensitive or heat-sensitive) material is deposited with
a first probe. a second probe is used to irradiate said deposit
with electromagnetic radiation or heat it locally. for example, the
second probe may be a near-field scanning optical microscopy (NSOM)
probe capable of delivering light and a scanning thermal microscopy
tip capable to locally heating the substrate.
[0356] in a fifth embodiment, a probe is used to deposit an ink in
an area of interest. the deposit is then submitted to
transformation means, while the deposition probe is kept away from
the substrate to pattern or is otherwise protected, so that curing
of the precursor ink on the probe itself is prevented. for example,
a laser beam may be used to irradiate the deposit and its vicinity,
curing it either thermally or optically (FIG. 27). the probe may be
shielded from laser radiation by moving it way from the illuminated
spot.
[0357] in another example, light is injected in the (transparent)
substrate, in such way that it is totally internally reflected in
proximity of the deposit, triggering e.g. its photoreduction or
photopolymerization. the probe may be retracted from the substrate
surface by a few microns to keep it off the evanescent wave.
[0358] in a third example, the deposition means is a hollow probe,
such as a nanopipette, which delivers a first ink. a second
compound is present on the substrate or delivered nearby (e.g. in a
gaseous form). Exposure of said first ink to said second compound
results in the (chemical) transformation of said first and/or
second on the substrate, but not within the nanopipette.
[0359] a fourth example involves a deposition probe kept thermally
cold while the substrate is heated to a temperature where the ink
being deposited transforms.
[0360] Preferred Embodiments:
[0361] in conclusion, the invention provides for a series of
preferred embodiments which include the following:
[0362] in embodiment 1, an article comprising at least one filled
nanometer-scale opening. in embodiment 2, the article of embodiment
1, wherein the nanometer-scale opening before being filled is a
defect. in embodiment 3, the article of claim 1, wherein the
nanometer-scale opening before being filled is a defect in a
photomask.
[0363] in embodiment 4, a method comprising filling one or more
nanometer-scale opening(s). in embodiment 5, the method of
embodiment 4, wherein the filling occurs by using a
nanolithographic or nanofabrication method; in the embodiment 6,
the method of embodiment 5, wherein the nanolithographic method
comprises a deposition nanolithographic method; in embodiment 7,
the method of embodiment 5, wherein the nanolithographic method
comprises a direct write nanolithographic method. in embodiment 8,
the method of embodiment 5, wherein the nanolithographic method
comprises nanografting, meniscus nanografting, pick-and-place
nanolithography, or nanopen reader writer; in embodiment 9, the
method of any of embodiments 6-8, wherein the nanolithographic
method comprises use of a material being deposited which comprises
a metal. in embodiment 10, the method of any of embodiments 6-8,
wherein the nanolithographic method comprises use of a material
being deposited which comprises chromium, cobalt, nickel, tungsten,
molybdenum or silver. in embodiment 11, the method of any
embodiments 6-8, wherein the nanolithographic method comprises use
of a material being deposited which is a metal oxide or a metal
particle-containing solution. in embodiment 12, the method of any
embodiment 6-8, wherein the nanolithographic method comprises use
of a material being deposited which is opaque to electromagnetic
radiation. in embodiment 13, the method of any embodiments 4-12,
wherein the method comprises nanolithographic printing comprising
use of a substrate which is a photomask.
[0364] in embodiment 14, the method for photomask repair comprising
adding material to a defective photomask by direct write
nanolithography with use of a scanning probe microscopic tip. in
embodiment 15, the method according to embodiment 14, wherein the
material is an optically transparent material upon the adding. in
embodiment 16, the method according to embodiment 14, wherein the
material is an optically opaque material upon adding. in embodiment
17, the method for photomask fabrication comprising adding material
to a substrate to form a photomask by direct write nanolithography
with use of a scanning probe microscopic tip.
[0365] in embodiment 18, a method for nanolithography comprising
(1) providing a photomask substrate having at least one defect, (2)
providing a scanning probe microscope tip, wherein the tip is
coated with a patterning compound, (3) contacting the coated tip
with the photomask substrate so that the compound is applied to the
substrate so as to repair at least one defect.
[0366] in embodiment 19, a method for nanolithography comprising
(1) providing a photomask substrate having at least one defect, (2)
providing a scanning probe microscope tip, wherein the tip is
coated with a patterning compound, (3) using the coated tip to
apply the compound to the substrate so as to repair at least one
defect.
[0367] in embodiment 20, a method for nanolithography comprising
(1) providing a photomask substrate having at least one defect, (2)
providing a scanning probe microscope tip, wherein the tip is
coated with a patterning compound, (3) contacting the coated tip
with the photomask substrate so that the compound is added to the
substrate.
[0368] in embodiment 21, a method for nanolithography comprising
(1) providing a photomask substrate having at least one defect, (2)
providing a scanning probe microscope tip, wherein the tip is
coated with a patterning compound, (3) using the coated tip to add
the compound to the substrate.
[0369] in embodiment 22, a method for nanolithography comprising
using a coated scanning probe microscopic tip to deposit a
patterning compound on a substrate in forming a photomask.
[0370] in embodiment 23, a method of inspecting and modifying an
object using SPM technology, the method comprising the steps
of:
[0371] inspecting the object by making SPM measurement of the
object with a first SPM probe;
[0372] generating modification data from the SPM measurements that
identifies a modification to be performed on the object's material;
and
[0373] in response to the modification data, performing the
modification by adding material to the object's material with the
first SPM probe or with a second SPM probe,
[0374] wherein the adding of material is carried out by direct
write nanolithographic printing by transfer of the material from
the probe tip to the object.
[0375] in embodiment 24, the method according to embodiment 23,
wherein the modification includes at least a structural
modification of the object's material or a chemical modification of
the object's material, and
[0376] in embodiment 25, a method of inspecting and modifying an
object using SPM technology, the method comprising the steps
of:
[0377] inspecting the object by making SPM measurement of the
object with a first SPM probe;
[0378] generating modification data from the SPM measurements that
identifies a modification to be performed on the object's material;
and
[0379] in response to the modification data, performing the
modification by adding material to the object's material with the
first SPM probe or with a second SPM probe,
[0380] wherein either the first SPM probe or the second SPM probe
is an atomic force microscope tip coated with an ink which is the
material added to the object's material.
[0381] in embodiment 26, a system for inspecting and modifying an
object using SPM technology, the system comprising:
[0382] a set of SPM probes, including a probe used for inspecting
which is configured to make one or more SPM measurements and a
probe used for modifying which is configured to add material to the
object's material, the probe used for inspecting and the probe used
for modifying being the same probe or being separate probes;
[0383] a first component configured to inspect the object by making
SPM measurements of the object using the probe used for
inspecting;
[0384] a second component configured to generate modification data
from the SPM measurements that identifies a modification to be
performed on the object's material; and
[0385] a third component configured to perform the modification by
adding material to the object's material using the probe used for
modifying, in accordance with the modification data;
[0386] wherein the adding of material is carried out by direct
write nanolithographic printing.
[0387] in embodiment 27, a system for inspecting and modifying an
object using SPM technology, the system comprising:
[0388] a set of SPM probes, including a probe used for inspecting
which is configured to make one or more SPM measurements and a
probe used for modifying which is configured to add material to the
object's material, the probe used for inspecting and the probe used
for modifying being the same probe or being separate probes;
[0389] a first component configured to inspect the object by making
SPM measurements of the object using the probe used for
inspecting;
[0390] a second component configured to generate modification data
from the SPM measurements that identifies a modification to be
performed on the object's material; and
[0391] a third component configured to perform the modification by
adding material to the object's material using the probe used for
modifying, in accordance with the modification data;
[0392] wherein the probe used for modifying is an atomic force
microscope tip coated with an ink which is the material added to
the object's material.
[0393] in embodiment 28, a method for repairing a phase shift mask
comprising (1) providing a phase shift mask, (2) providing a
scanning probe microscope tip, wherein the tip is coated with a
patterning compound, (3) using the coated tip to apply the compound
to the mask so as to adjust a phase shift of radiation to be passed
through the mask to 180 degrees.
[0394] in embodiment 29, the method of embodiment 28, wherein the
tip comprises an AFM tip.
[0395] in embodiment 30, the method of embodiment 29, wherein the
mask comprises a strong phase shift mask and the patterning
compound adjusts a height of a transparent window in the mask.
[0396] in embodiment 31, the method of embodiment 29, wherein the
mask comprises an attenuating phase shift mask and the patterning
compound adjusts a height of a partially transmitting material on
the mask.
[0397] in embodiment 32, a method for repairing an interconnect
metallization over a solid state device comprising (1) providing a
solid state device comprising an interconnect metallization, (2)
providing a scanning probe microscope tip, wherein the tip is
coated with a patterning compound, (3) using the coated tip to
apply the compound to the metallization so as to fill an opening in
the metallization.
[0398] in embodiment 33, a method of embodiment 32, wherein the tip
comprises an AFM tip and the solid state device comprises a
semiconductor device.
[0399] in embodiment 34, a method for forming a gate insulating
layer of a field effect transistor, comprising providing a scanning
probe microscope tip over a transistor channel, wherein the tip is
coated with a patterning compound, using the coated tip to apply
the a precursor compound to the channel and converting the
precursor material to the gate insulating layer.
[0400] in embodiment 35, the method of embodiment 34, further
comprising forming a gate electrode over the gate insulating
layer.
[0401] in embodiment 36, the method of embodiment 35, wherein the
gate insulating layer comprises silicon oxide.
[0402] in embodiment 37, a method for repairing a MEMS comprising
(1) providing the MEMS, (2) providing a scanning probe microscope
tip, wherein the tip is coated with a patterning compound, (3)
using the coated tip to apply the compound to the MEMS to repair
the MEMS.
[0403] Embodiment 38 is a method for depositing a material on a
substrate comprising:
[0404] providing a tip comprising an elastomer at the tip end;
[0405] providing a patterning compound at the tip end;
[0406] providing a substrate;
[0407] depositing the patterning compound from the tip end to the
substrate.
[0408] Embodiment 39 is the method according to embodiment 38,
wherein the elastomer is a hydrophobic polymer. Embodiment 40 is a
method according to embodiment 38, wherein the tip is a scanning
probe microscope tip. Embodiment 41 is a method according to
embodiment 38, wherein the tip is an atomic force microscope tip.
Embodiment 42 is a method according to embodiment 38, wherein the
substrate is a defective mask. Embodiment 43 is a method according
to claim 38, wherein the patterning compound is a photomask repair
ink. Embodiment 44 is a method according to embodiment 38, wherein
the depositing step is used to fabricate a photomask for
microlithography.
[0409] Embodiment 45 is a method of improving the deposition of
materials from a tip comprising the step of modifying the tip with
an elastomer. Embodiment 46 is a method according to embodiment 45,
wherein the elastomer is a hydrophobic siloxane elastomer.
Embodiment 47 is a method according to embodiment 45, wherein the
tip is modified by coating the tip with an elastomer precursor and
then converting the precursor to the elastomer. Embodiment 48 is a
method according to embodiment 45, wherein the tip is a scanning
probe microscope tip. Embodiment 49 is a method according to
embodiment 45, wherein the tip is an atomic force microscope
tip.
* * * * *